Transmission with first and second transmission elements

ABSTRACT

A transmission includes a first component, a second component, and first and second transmission elements. The first component has a drive member and a portion configured to be actuated to inhibit movement of the drive member. The first and second transmission elements are each coupled to the drive member and the second component and configured to cause movement of at least one of the first component and the second component in response to movement of the drive member. At least one of the first and second transmission elements includes a first plurality of transmission sub-elements.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationSer. No. 61/203,475, filed on Dec. 23, 2008, which is herebyincorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates to a transmission, particularly a tensionelement drive system for a robotic arm.

2. Description of Related Art

Robotic systems are often used in applications that require a highdegree of accuracy and/or precision, such as surgical procedures orother complex tasks. Such systems may include various types of robots,such as autonomous, teleoperated, semi-active, passive, and interactive.For example, in joint replacement surgery, a surgeon can use aninteractive, haptically guided robotic arm in a passive manner to sculptbone to receive a joint implant, such as a knee implant. To sculpt bone,the surgeon manually grasps and manipulates the robotic arm to move acutting tool (such as a burr) that is coupled to the robotic arm. Aslong as the surgeon maintains the cutting tool within a predefinedvirtual cutting boundary, the robotic arm moves freely with low frictionand low inertia such that the surgeon perceives the robotic arm asweightless and can move the robotic arm as desired. If the surgeonattempts to cut outside the virtual cutting boundary, however, therobotic arm provides haptic (or force) feedback that prevents orinhibits the surgeon from moving the cutting tool beyond the virtualcutting boundary. In this manner, the robotic arm enables highlyaccurate, repeatable bone cuts.

The ability of a robotic arm to function in the above-described manneris dependent on the drive system (also called the drive train or drivetransmission) of the robotic arm. Ideally, the drive system ischaracterized by low friction, low inertia, high stiffness, largebandwidth, near-zero backlash, force fidelity, and/or backdrivability. Aflexible transmission, such as a tension element drive system, may havethese characteristics. One difficulty with conventional tension elementdrive systems, however, is that they may not be sufficiently fail-safefor use in surgical applications where failure of the drive system couldendanger a patient. For example, failure of one tension element (e.g., acable or cord) in the drive system could result in unintended movementof the robotic arm that could harm the patient. To improve safety, therobotic arm can include joint brakes to constrain movement of the jointsof the robotic arm in the event of a tension element failure.Incorporation of joint brakes, however, increases the weight and inertiaof the robotic arm, which adversely impacts backdrivability and hapticresponse.

Another difficulty with conventional tension element drive systems isthat the tension elements must be pre-tensioned to eliminate slack thatmay cause backlash. Pre-tensioning loads, however, are about 15% to 50%of the breaking strength of the tension element, which imparts largeforces to drive system components, bearings, and support structure. Thehigh load also increases friction forces in the drive system componentsand contributes to surgeon fatigue.

Another difficulty with conventional tension element drive systems isthat such drive systems may not be easily manufactured, serviced, and/orupgraded. For example, a conventional tension element drive system maybe an integral system in the sense that components in one part of thedrive system (e.g., in one joint) are, to some degree, dependent on orimpacted by components in another part of the drive system (e.g., inanother joint). Thus, if one portion of the drive system is defective,it may be necessary to dismantle other portions of the drive system thatare functioning properly in order to repair the defective portion. Forexample, repairing a problem in one joint of the robotic arm may requirede-cabling multiple joints of the robotic arm. The inability to isolateportions of a conventional tension element drive system increases thetime and labor required to service and upgrade the robotic arm, whichresults in costly repairs and lengthy downtime that reduces a hospital'sability to optimize use of the robotic arm.

SUMMARY

An embodiment of a transmission according to the present inventionincludes a first component, a second component, and first and secondtransmission elements. The first component has a drive member and aportion configured to be actuated to inhibit movement of the drivemember. The first and second transmission elements are each coupled tothe drive member and the second component and configured to causemovement of at least one of the first component and the second componentin response to movement of the drive member. At least one of the firstand second transmission elements includes a first plurality oftransmission sub-elements.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated and constitute a partof this specification, illustrate embodiments of the invention andtogether with the description serve to explain aspects of the invention.

FIG. 1 is a perspective view of a surgical system according to anembodiment.

FIG. 2 is a perspective view of an embodiment of a robotic arm of thesurgical system of FIG. 1.

FIG. 3 is a perspective view of the robotic arm of FIG. 2 withprotective covers removed.

FIG. 4 is a perspective view of the robotic arm of FIG. 2 withprotective covers removed and showing modular construction.

FIG. 5A is a front perspective view of an embodiment of a first moduleof the robotic arm of FIG. 2.

FIG. 5B is a rear perspective view of the first module of FIG. 5A.

FIG. 5C is a right side elevation view of the first module of FIG. 5A.

FIG. 5D is a left side elevation view of the first module of FIG. 5A.

FIG. 5E is a rear elevation view of the first module of FIG. 5A

FIG. 6 is a perspective view of an embodiment of a joint assembly of thefirst module of FIG. 5A.

FIG. 7A is a cross-sectional view of an embodiment of a drive member ofthe joint assembly of FIG. 6.

FIG. 7B is a side elevation view of an embodiment of a motor shaft andpinion of the joint assembly of FIG. 6.

FIG. 8A is an elevation view of an embodiment of a flexible transmissioncoupled to a drive member of the joint assembly of FIG. 6.

FIG. 8B is an elevation view of an embodiment of a flexible transmissioncoupled to a connection mechanism of the joint assembly of FIG. 6.

FIGS. 9A and 9B are top perspective views of the connection mechanism ofFIG. 8B.

FIG. 10 is a cross-sectional view of an embodiment a joint output of ajoint assembly of the first module of FIG. 5A.

FIG. 11 is an elevation view of an embodiment of a flexible transmissioncoupled to a driven member of the first module of FIG. 5A.

FIG. 12 is a perspective view of a second module according to anembodiment.

FIG. 13 is a perspective view of an embodiment of a joint assembly ofthe second module of FIG. 12.

FIG. 14A is a schematic of an embodiment of first and second stageflexible transmissions of the second module of FIG. 12.

FIG. 14B is a force diagram of an embodiment of a tension elementconfiguration of the second module of FIG. 12.

FIG. 14C is a schematic of a conventional tension element configuration.

FIG. 14D is a force diagram of the conventional tension elementconfiguration of FIG. 14C.

FIGS. 15 and 16 are perspective views of an embodiment a driven memberof the second module of FIG. 12.

FIG. 17 is a perspective view of an embodiment of a motor shaft andpinion of the second module of FIG. 12.

FIG. 18 is a top perspective view of an embodiment of a connectionmechanism of the second module of FIG. 12.

FIG. 19A is a cross-sectional view of an embodiment of a drive member ofthe second module of FIG. 12.

FIG. 19B is a schematic of an embodiment of a flexible transmissioncoupled to a drive member of the second module of FIG. 12.

FIG. 20 is a cross-sectional view of an embodiment of a drive member ofthe second module of FIG. 12.

FIG. 21 is a cross-sectional view of an embodiment of a driven member ofthe second module of FIG. 12.

FIG. 22A is a perspective view of a third module according to anembodiment.

FIG. 22B is a cross-sectional view of the third module of FIG. 22A.

FIG. 22C is a perspective view of an embodiment of a flexibletransmission of the third module of FIG. 22A.

FIG. 23 is a cross-sectional view of an embodiment a drive member of thethird module of FIG. 22A.

FIG. 24 is a side elevation view of an embodiment of a motor shaft andpinion of the third module of FIG. 22A.

FIGS. 25A-25C are perspective views of an embodiment of a connectionmechanism of the third module of FIG. 22A.

FIG. 26 is a front perspective view of an embodiment an adjustmentmember of the third module of FIG. 22A.

FIG. 27A is a front perspective view of an embodiment of an adjustmentmember of the third module of FIG. 22A.

FIG. 27B is a front elevation view of the adjustment member of FIG. 27A.

FIG. 28A is a top perspective view of a fourth module according to anembodiment.

FIG. 28B is a perspective view of an embodiment of a flexibletransmission of the fourth module of FIG. 28A.

FIG. 28C is a bottom perspective view of the fourth module of FIG. 28A

FIG. 28D is a perspective view of an embodiment of a flexibletransmission of the fourth module of FIG. 28A.

FIG. 28E is a cross-sectional view of the fourth module of FIG. 28A.

FIG. 29 is a cross-sectional view of an embodiment a drive member of thefourth module of FIG. 28A.

FIG. 30 is a schematic of an embodiment of a flexible transmissioncoupled to a drive member of the fourth module of FIG. 28A.

FIG. 31A is a cross-sectional view of an embodiment of a driven memberof the fourth module of FIG. 28A.

FIG. 31B is a top view of an embodiment of a pulley of the fourth moduleof FIG. 28A.

FIG. 31C is a perspective view of an embodiment of a pulley of thefourth module of FIG. 28A.

FIG. 31D is a perspective view of an embodiment of a joint encoder ofthe fourth module of FIG. 28A.

FIG. 32 is a side elevation view of a stand assembly according to anembodiment.

FIG. 33A is a side elevation view of a lift assembly in a mobileconfiguration according to an embodiment.

FIG. 33B is a side elevation view of the lift assembly of FIG. 33A in astationary configuration.

FIG. 33C is a cross-sectional view of a leg member of a lift assemblyaccording to an embodiment.

FIG. 33D is a cross-sectional view of a leg member of a lift assemblyaccording to an embodiment.

FIG. 34 is a schematic of a double connector tension element accordingto an embodiment.

FIG. 35 is a schematic of a triple connector tension element accordingto an embodiment.

FIG. 36A is a schematic of the triple connector tension element of FIG.35 coupled to a drive member and a driven member according to anembodiment.

FIG. 36B is a schematic of the triple connector tension element of FIG.35 coupled to a drive member and a driven member according to anembodiment.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Presently preferred embodiments of the invention are illustrated in thedrawings. An effort has been made to use the same or like referencenumbers throughout the drawings to refer to the same or like parts.Although this specification refers primarily to a robotic arm fororthopedic procedures, it should be understood that the subject matterdescribed herein is applicable to other types of robotic systems,including those used for surgical and non-surgical applications, as wellas to non-robotic systems that include flexible transmissions.

Overview

A robotic system for surgical applications according to the presentinvention preferably includes a robotic arm that is used in aninteractive manner by a surgeon to perform a surgical procedure on apatient. In a preferred embodiment the robotic system is the RIO®Robotic Arm Interactive Orthopedic System manufactured by MAKO SurgicalCorp. of Fort Lauderdale, Fla. The robotic arm is preferably a hapticdevice that works in combination with a computer aided navigation systemand a tracking device. For example, as described in U.S. patentapplication Ser. No. 11/357,197 (Pub. No. US 2006/0142657), filed Feb.21, 2006, and hereby incorporated by reference herein in its entirety, asurgical tool, such as a cutting burr, is coupled to the robotic arm.The surgeon manually moves the robotic arm to manipulate the surgicaltool to perform a surgical task on the patient, such as bone cutting fora joint replacement operation. As the surgeon manipulates the tool, therobotic arm provides haptic (or force) feedback to limit the surgeon'sability to move the cutting tool beyond a predefined virtual cuttingboundary, which results in highly accurate and repeatable bone cuts. Therobotic arm works in a passive manner and provides haptic feedback onlywhen the surgeon attempts to cut bone that lies outside the virtualcutting boundary. The haptic feedback is generated by one or moreactuators (e.g., motors) in the robotic arm and is transmitted to thesurgeon via a flexible transmission, such as a tension elementtransmission. When the robotic arm is not providing haptic feedback, therobotic arm 10 is freely moveable by the surgeon.

Exemplary Robotic Arm Devices

FIG. 1 shows an example of a surgical system 5 that includes a roboticarm 10 according to an embodiment of the invention. The surgical system5 may also include a computer aided navigation system 2 and a trackingdevice 3. The robotic arm 10 includes one or more joint assemblies thatprovide, for example, rotational degrees of freedom of movement. Asillustrated in FIGS. 2 and 3, the robotic arm 10 includes a first jointassembly 100 that provides a first rotational degree of freedom (DOF)J1, a second joint assembly 200 that provides a second rotational DOFJ2, a third joint assembly 300 that provides a third rotational DOF J3,a fourth joint assembly 400 that provides a fourth rotational DOF J4, afifth joint assembly 500 that provides a fifth rotational DOF J5, and asixth joint assembly 600 that provides a sixth rotational DOF J6. An endeffector 700 is coupled to the output of the sixth joint assembly 600.As described further below, each of the joint assemblies 100, 200, 300,400, 500, 600 includes a first component having a drive member, a secondcomponent, and first and second transmission elements each coupled tothe first component and the second component and configured to causemovement of at least one of the first and second components in responseto movement of the drive member. Although the embodiment of FIGS. 1-3includes six degrees of freedom, the robotic arm 10 may include more orfewer degrees of freedom depending on the application for which therobotic arm 10 will be used.

Each rotational degree of freedom has a positive direction (indicated bythe arrows in FIG. 2) and an opposite negative direction and preferablyhas a limited total range of motion. For example, in an exemplaryembodiment, a range of motion of the first joint assembly 100 is about250 degrees, a range of motion of the second joint assembly 200 is about40 degrees, a range of motion of the third joint assembly 300 is about270 degrees, a range of motion of the fourth joint assembly 400 is about100 degrees, a range of motion of the fifth joint assembly 500 is about270 degrees, and a range of motion of the sixth joint assembly 600 isabout 260 degrees. These exemplary ranges of motion provide the roboticarm 10 with sufficient dexterity for tasks requiring high accuracy andprecision, such as surgery. Additionally, the exemplary ranges of motionenable the robotic arm 10 to be manipulated by both right and lefthanded users. For example, the robotic arm 10 shown in FIG. 2 isconfigured for a right handed user. Typically, to manipulate the roboticarm 10, a right handed user will place his or her right hand on the endeffector 700 and his or her left hand on either a handle 24 located onthe fifth joint assembly 500 or projections 26 located on the sixthjoint assembly 600. This configuration, however, does not work well fora left handed user because the user cannot easily grasp the end effector700 with his or her left hand. To reconfigure the robotic arm 10 for aleft handed user, the robotic arm 10 is symmetrically flipped from thepose shown in FIG. 2. In particular, in the left handed configuration,relative to FIG. 2, the first rotational DOF J1 is 180 degrees from thatshown, the third rotational degree of freedom J3 is −180 degrees fromthat shown, the fifth rotational degree of freedom J5 is −180 degreesfrom that shown, and the sixth rotational degree of freedom J6 is 180degrees from that shown.

To protect the mechanisms of the joint assemblies from damage and/orcontamination and to shield the surgeon from potential hazards (e.g.,pinch hazards), the robotic arm 10 includes protective covers 20. Asshown in FIG. 2, the protective covers 20 encase the joint assemblies.In contrast, FIG. 3 shows the robotic arm 10 with the protective covers20 removed and the joint assemblies exposed. The protective covers 20may be formed of rigid plastic, such as molded plastic sheeting made ofa durable thermoplastic alloy. In addition to rigid protective covers,the robotic arm 10 may also include flexible covers, such as a bellows22. As shown in FIG. 3, the bellows 22 covers a gap between the fourthand fifth joint assemblies 400, 500 to simultaneously protect thesurgeon from pinch hazards and allow the gap to expand and contract overthe range of motion of the fourth joint assembly 400.

Preferably, the robotic arm 10 has a modular design where one or more ofthe joint assemblies comprise modules that can be independentlymanufactured and tested before being integrated with the remaining jointassemblies. Modularity advantageously improves manufacturing workflow,especially for high volume production. Modularity also improvesserviceability by enabling service personnel to replace only those jointassemblies that require replacement. In addition, modularity enables therobotic arm 10 to be upgraded in the field by replacing one or moreexisting modular joint assemblies with alternative modular jointassemblies. For example, the degrees of freedom of the robotic arm 10can be increased or decreased by replacing one or more of the existingmodules with a module having a different design. In this manner,features of the robotic arm 10 can be tailored for each applicationwithout requiring changes to the overall design of the robotic arm 10.The number of modules and the characteristics of each can be determinedbased upon various factors, such as desired physical and performancecharacteristics. For example, in one embodiment, the robotic arm 10 hasfour modules. As shown in FIG. 4, a first module A includes the first,second, and third joint assemblies 100, 200, 300. A second module Battaches to the first module A and includes the fourth joint assembly400. A third module C attaches to the second module B and includes thefifth joint assembly 500. A fourth module D attaches to the third moduleC and includes the sixth joint assembly 600.

FIGS. 5A to 5E show the first module A according to an embodiment of theinvention. In this embodiment, the first module A includes the first,second, and third joint assemblies 100, 200, 300. As noted above, eachjoint assembly 100, 200, 300 provides one rotational degree of freedom.Thus, the first module A provides the first three degrees of freedom ofthe robotic arm 10. The output motion of the first module A is similarto the motion of a human shoulder joint. For this reason, the firstmodule A is also referred to as the robot shoulder. Preferredembodiments of the joint assemblies 100, 200, 300 will now be describedin detail. Specific descriptions of individual joint assemblies areexemplary only and are to be considered in all respects illustrativerather than limiting of the invention described herein. One skilled inthe art will realize the invention may be embodied in other specificforms without departing from the spirit or essential characteristicsthereof.

First Joint Assembly

FIG. 6 shows the first joint assembly 100 according to an embodiment ofthe invention. The first joint assembly 100 includes a first component101, a second component 102, and an at least partially flexibletransmission 103 (see FIG. 8A). In this embodiment, the first component101 includes a drive member 110 and a driven member 120. The flexibletransmission 103 is coupled to the drive member 110 and the secondcomponent 102. When actuated, the drive member 110 imparts rotationalmotion to the driven member 120 via the flexible transmission 103.

The flexible transmission 103 is configured to transmit force and/ortorque from the drive member 110 resulting in motion of the drivenmember 120. Preferably, the flexible transmission 103 is a tensionelement drive system (e.g., a cable, steel tape, or polymeric tendontransmission). In an exemplary embodiment, the flexible transmission 103is a cable drive system. Cable drive systems have advantages over othermechanical drive systems, such as gears and linkages, because cabledrive systems can be configured to provide low friction, low inertia,low compliance (i.e., high stiffness), large bandwidth, near-zerobacklash, force fidelity, and/or backdrivability. In one embodiment, theflexible transmission 103 includes a first transmission element having afirst plurality of transmission sub-elements and a second transmissionelement having a second plurality of transmission sub-elements. Thetransmission sub-elements are preferably tension elements, such ascables (or cords). In this embodiment, the first transmission element isa first cable set that includes the first plurality of transmissionsub-elements, which are a first cable 130 (i.e., a first transmissionsub-element) and a second cable 131 (i.e., a second transmissionsub-element). Similarly, the second transmission element is a secondcable set that includes the second plurality of transmissionsub-elements, which are a third cable 133 (i.e., a third transmissionsub-element) and a fourth cable 134 (i.e., a fourth transmissionsub-element). The cables 131, 132, 133, 134 may be any cablesappropriate for use in a robotic system but are preferably tungstencables. Although the cables 131, 132, 133, 134 can be configured in avariety of ways to impart motion to the driven member 120, in thisembodiment, each of the cables 131, 132, 133, 134 has a proximal endconnected to the drive member 110 and a distal end connected to thesecond component 102 via a connection mechanism 150. The secondcomponent 102 includes a main drive 140 that is stationary relative tothe first component 101. The manner in which motion is imparted to thedriven member 120 is explained below.

In this embodiment, the driven member 120 is the joint output of thefirst joint assembly 100. As shown in FIG. 6, the driven member 120includes a riser assembly 142 that can be coupled to a baseplate 144 by,for example, a cross roller bearing 146. For example, an inner race ofthe cross roller bearing 146 is connected to the baseplate 144, and anouter race of the cross roller bearing 146 is connected to the riserassembly 142. The cross roller bearing 146 is a precision bearing thatenables the riser assembly 142 to rotate with low friction relative tothe baseplate 144. To limit rotation of the riser assembly 142, hardstops 148 a are disposed on the riser assembly 142 and correspondinghard stop bumpers 148 b are disposed on the baseplate 144. When rotationof the riser assembly 142 causes one of the hard stops 148 a to contactone of the hard stop bumpers 148 b, rotation of the riser assembly 142is constrained. As discussed further below, the driven member 120 (i.e.,the riser assembly 142) is preferably unbraked, meaning that the drivenmember 120 does not have a brake mechanism.

Rotation of the riser assembly 142 is driven by the drive member 110. Inthis embodiment, the drive member 110 includes a drive motor 112 that isdisposed on the riser assembly 142 and thus moves with the riserassembly 142 as the riser assembly 142 rotates. To cause the riserassembly 142 to rotate, the drive motor 112 includes a motor shaft 114having a pinion 116 extending therefrom, as shown in FIGS. 7A and 7B.The pinion 116 is configured to engage the flexible transmission 103.For example, each of the cables 131, 132, 133, 134 has a proximal endconnected to and wound around the pinion 116 and a distal end connectedto the main drive 140. The main drive 140 is disposed within the riserassembly 142 and is rigidly fixed to the baseplate 144. Thus, the maindrive 142 is stationary relative to the baseplate 144 whereas the riserassembly 142 rotates relative to the baseplate 144. As shown in FIGS. 8Aand 8B, the first and second cable sets extend from the pinion 116 inopposite directions around the main drive 140 and connect to the maindrive 140 at the connection mechanism 150. When the drive motor 112 isactuated, the pinion 116 rotates causing the first cable set to windaround (or unwind from) the pinion 116 and the second cable set toconversely unwind from (or wind around) the pinion 116 depending on thedirection of rotation. Because the distal ends of the cables 131, 132,133, 134 are connected to the main drive 140 and the main drive 140 isstationary relative to the riser assembly 142, the winding and unwindingof the cables 131, 132, 133, 134 exerts force and/or torque on the riserassembly 142 that causes the riser assembly 142 to rotate around themain drive 140 thereby providing the first rotational degree of freedomJ1 shown in FIG. 2. In this manner, the first and second transmissionelements are configured to cause movement of the first component 101 inresponse to movement of the drive member 110.

Preferably, the joint output (in this case, the riser assembly 142,which is the driven member 120) includes a joint encoder configured tomeasure angular rotation of the joint output. In one embodiment, thejoint encoder includes an encoder scale 160 that rotates with the riserassembly 142 and an encoder read head 162 that reads the encoder scale160 (see FIG. 6). Although any suitable encoder system can be used, inthis embodiment, the joint encoder is a tape scale type encoder system.When using a tape scale type encoder system in a rotary application, thecircularity of the mounting surface to which the encoder scale 160 isaffixed is important for obtaining accurate encoder readings. To ensuresufficient circularity, the encoder scale 160 is preferably mounted toan outside diameter or periphery of the cross roller bearing 146, wherethe outside diameter is precision ground (e.g., with a run-out toleranceof less than 11 micrometers) after assembly of the cross roller bearing146. The encoder scale 160 can be attached to the cross roller bearing146 using, for example, a pressure sensitive adhesive. To preventdelamination of the encoder scale 160 from the cross roller bearing 146,ends of the encoder scale 160 can be fixed under a tape scale clamp (notshown) that clamps the ends to the cross roller bearing 146, forexample, using a screw fastener. The encoder read head 162 is mounted onthe baseplate 144 so as to have a line of sight to the encoder scale160. As the riser assembly 142 and outer race of the cross rollerbearing 146 rotate, the encoder read head 162 reads the encoder scale160 to determine relative angular position of the riser assembly 142.Because the joint encoder is a relative, as opposed to an absolute,encoder system, the joint encoder also includes an encoder index mark(not shown) disposed on the riser assembly 142. The encoder index markincludes a magnet that provides a fixed reference, or index mark, forthe joint encoder so the robotic arm 10 knows the rotational location ofthe joint output relative to a known index location. Advantageously, thejoint encoder enables rotational output of the joint output to bemeasured. As discussed further below, the rotational output can becompared to the rotational input from the drive motor 112 to evaluatethe integrity of the flexible transmission 103.

As noted above, the drive member 110 includes a drive motor 112 (oractuator) that imparts rotational motion to the driven member 120 viathe flexible transmission 103. The drive motor 112 may be any motorsuitable for driving the driven member. In one embodiment, the drivemotor 112 is a brushless DC permanent magnet motor, although the drivemotor 112 could also be a brush-type motor or other motor technology. Asshown in FIGS. 7A and 7B, in this embodiment, the drive motor 112includes a housing 117, a stator 118 bonded to the housing 117, and arotor 119 bonded to the motor shaft 114. The motor shaft 114 issupported in the housing 117 by motor bearings, such as angular contactball bearings or any appropriate bearing that reduces friction andpermits free rotation of the motor shaft 114 relative to the housing117. A jam nut and lock nut (collectively 113) thread onto the motorshaft 114 to draw the motor shaft 114 through the housing 117 untilaxial clearance in the motor bearings is taken up. As a result, themotor bearings are pre-loaded, which eliminates axial and radial play ofthe motor shaft 114 relative to the housing 117. The jam nut preventsloosening of the lock nut over time (e.g., due to vibration).

Preferably, the drive motor 112 includes a motor encoder configured tomeasure angular rotation of the motor shaft 114. Similar to the jointencoder, the motor encoder includes an encoder scale 115 a that rotateswith the motor shaft 114 and an encoder read head 115 b that reads theencoder scale. In one embodiment, the encoder scale 115 a is a circularglass scale with fine pitch marks etched in the glass. The encoder scale115 a is bonded to a precision hub that is attached to the motor shaft114. As shown in FIG. 7A, the encoder read head 115 b is mounted so asto have a line of sight to the encoder scale 115 a. As the motor shaft114 and encoder scale 115 a rotate, the encoder read head 115 b readsthe pitch marks on the encoder scale 115 a to determine relative angularposition of the motor shaft 114. Thus, the motor encoder enablesmeasurement of the rotation of the motor shaft 114. As a result, theangular rotational input provided by the drive motor 112 (measured bythe motor encoder) can be compared to the angular rotational output ofthe joint output (measured by the joint encoder). The rotational outputshould be proportional to the rotational input multiplied by the inverseof the drive ratio (drive reduction) of the first joint assembly 100. Adiscrepancy between the rotational input and output may indicate aproblem with the flexible transmission 103 and can be used to trigger afault in the robotic arm 10 that alerts the user of the discrepancy,places the robotic arm 10 in a safe mode and/or causes otherprecautionary action to be taken. Problems that might cause adiscrepancy include failure of a cable, a cable tensioning mechanism, atransmission element such as a pinion or pulley, and the like.Advantageously, the combined use of motor and joint encoders contributesto overall failsafe operation of the robotic arm 10.

In an exemplary embodiment, the drive motor 112 includes a portionconfigured to be actuated to inhibit movement of the drive member, suchas a motor brake 111, as shown in FIG. 7A. The motor brake 111 may beany suitable motor brake assembly, such as a brake assembly manufacturedby The Carlyle Johnson Machine Company LLC, Bolton, Conn. The motorbrake 111 includes a rotor affixed to the motor shaft 114 and a brakebody attached to the motor housing 117 via an end cap. If power isapplied to the motor brake 111, the brake rotor is free to rotate andthe motor shaft 114 and pinion 116 can turn freely. If power is removedfrom the motor brake 111, the brake rotor, which is rigidly attached tothe motor shaft 114, is constrained from rotating, which inhibitsmovement of the motor shaft 114 and pinion 116. The motor brake 111 canbe engaged, for example, in response to a fault signal, such as a faultsignal indicating a discrepancy between the rotational input and outputof the first joint assembly 100.

The motor shaft 114 of the drive motor 112 is connected to (e.g.,coupled to or integral with) the pinion 116. As noted above, the pinion116 is configured to engage the flexible transmission 103. In oneembodiment, the drive member 110 includes a first interface configuredto removably secure the first transmission element and a secondinterface configured to removably secure the second transmissionelement. The first and second interfaces may be attachment elements 170.For example, the pinion 116 can include an attachment element 170 foreach of the cables 131, 132, 133, 134. The attachment element 170 is apoint of attachment for securing the proximal end of a cable to thepinion 116. The attachment element 170 may have any configurationsuitable for securely anchoring a cable to the pinion 116. In oneembodiment, the proximal end of the cable has a connector 4 (such as astainless steel or brass ball as shown in FIG. 34) swaged thereto, andthe attachment element 170 is configured to seat the connector 4 whenthe cable is under tension. For example, as shown in FIGS. 7A and 7B,the attachment element 170 includes an outer leg 171 and an inner leg172 extending radially from the pinion 116 and forming an aperture 173.One side of the aperture 173 has a contoured opening 174 large enough toreceive the connector 4 with the remaining portion of the aperture 173being wide enough to receive the cable but not wide enough to permit theconnector 4 to pass through the aperture 173. When the connector 4 isfitted into the contoured opening 174, the cable is passed through theaperture 173, and tension is applied to the cable in a direction awayfrom the connector 4, the connector 4 seats into the contoured opening174. As long as sufficient tension is maintained on the cable, theconnector 4 remains seated. The cable can be decoupled from theattachment element 170 by releasing sufficient tension from the cable.

As shown in FIGS. 7B and 8A, the portion of a cable that exits anattachment element 170 engages a guide 180 (individual guides are shownas 180 a and 180 b). The guide 180 is configured to locate the cable onthe pinion 116 and to direct and orient the cable. In one embodiment,the guide 180 comprises a groove (or channel) cut into the pinion 116.Preferably, the groove is a spiral (e.g., helical) groove that extendsalong a length of the pinion 116. The guide 180 receives the cable and,as the cable winds around the pinion 116, locates and constrains thecable. As shown in FIGS. 8A and 8B, each cable eventually leads off thepinion 116 and wraps around a portion of the main drive 140 beforeterminating at the connection mechanism 150 located on the main drive140.

Preferably, the pinion 116 is configured to secure and guide each of thecables 131, 132, 133, 134 in the manner described above. In particular,the pinion 116 includes an attachment element 170 for each of the cables131, 132, 133, 134. Two attachment elements 170 are disposed on aproximal end of the pinion 116 for interconnection with the cables 131,132, and two of the attachment elements 170 are disposed on a distal endof the pinion 116 for interconnection with the cables 133, 134. In thisembodiment, the pinion 116 includes two guides, where two of the cablesshare one guide and the other two cables share the other guide. Inparticular, the drive member 110 includes first and second guides 180 a,180 b configured to position the first and second transmissionsub-elements (i.e., the cables 131, 132) relative to the drive member110. The first and second guides 180 a, 180 b are also configured toposition the third and fourth transmission sub-elements (i.e., thecables 133, 134) relative to the drive member 110. For example, as shownin FIGS. 7B and 8A, the first guide 180 a is configured to locate thecable 131 and the second guide 180 b is configured to locate the cable132 (or vice versa), where the cables 131, 132 are secured to theproximal end of the pinion 116. Similarly, the first guide 180 a isconfigured to locate the cable 133 and the second guide 180 b isconfigured to locate the cable 134 (or vice versa), where the cables133, 134 are secured to the distal end of the pinion 116. Preferably,the first and second guides 180 a, 180 b extend along the length of thepinion 116 (i.e., the drive member 110) and are adjacent one anotheralong the length of the pinion 116. For example, the first guide 180 ais a first helical groove (or channel) and the second guide 180 b is asecond helical groove (or channel). These adjacent helical grooves forma “double helix” arrangement. As a result, as shown in FIG. 8A, thecables 131, 132 are disposed adjacent one another as they wind aroundthe pinion 116 from the proximal end toward the distal end. Similarly,the cables 133, 134 are disposed adjacent one another as they windaround the pinion 116 from the distal end toward the proximal end. Inthis embodiment, the first and second guides 180 a, 180 b are congruentin size and shape.

The attachment element and guide embodiments described above areexemplary. As will be apparent to one of skill in the art, the drivemember 110 could include alternative designs for attaching and guidingthe cables. One advantage of using adjacent helical grooves (or a“double helix” arrangement), however, is that such an arrangementenables the flexible transmission 103 to include two sets of cablescompactly packaged on a single pinion 116, where each cable set includesredundant cables (i.e., more than one cable performing the samefunction). For example, the cables 131, 132 are redundant because eachcable 131, 132 performs the same function of exerting a tension force onthe main drive 140 in a direction E when the pinion 116 rotates to windthe cables 131, 132 onto the pinion 116. Similarly, the cables 133, 134are redundant because each cable 133, 134 performs the same function ofexerting a tension force on the main drive 140 in a direction F when thepinion 116 rotates to wind the cables 133, 134 onto the pinion 116. Oneadvantage of redundancy is that even if one cable in a cable set fails(e.g., the cable 131), the second cable (e.g., the cable 132) continuesto transmit force and/or torque from the drive member 110 and therebymaintains control of the robotic arm 10. Thus, redundant tensionelements are a failsafe feature to ensure that failure of a singletension element will not result in an uncontrolled joint output. This isparticularly advantageous in surgical applications where malfunction ofthe robotic arm 10 during surgery could create a potentially dangerouscondition for the patient. Additionally, use of a second cable mayincrease coupling stiffness, which advantageously increases hapticstiffness.

Another advantage of failsafe redundant tension elements is that usingredundant tension elements in combination with a braked drive member(e.g., the drive motor 112 with the motor brake 111) enables the use ofan unbraked driven member, meaning that the driven member 120 (i.e., theriser assembly 140, which is the joint output) does not have a brakemechanism. A joint brake can be omitted because the drive member 110incorporates a brake and failure of a single tension element in aredundant tension element set will not result in uncontrolled jointoutput. As a result, motion of the first joint assembly 100 can beadequately controlled even if one tension element fails so there is noneed to be able to independently brake the joint output. Omitting ajoint brake improves performance of the robotic arm 10 because problemsassociated with conventional joint brakes are eliminated. In particular,a joint brake imparts high gravity and inertia loads on the jointassembly, which adversely impacts backdrivability and haptic response.Replacing a joint brake with a smaller brake on the drive member 110 andredundant tension elements advantageously decreases weight and inertiaand improves backdrivability and haptic response.

As shown in FIGS. 8A and 8B, the first and second cable sets extend fromthe pinion 116 in opposite directions around the main drive 140 andconnect to the main drive 140 at the connection mechanism 150. Althoughthe connection mechanism 150 is disposed on the main drive 140, which isa stationary component of the first joint assembly 100, it will beapparent to those of skill in the art that the connection mechanism 150could also be used on a moving member, such as a rotating pulley. Forease of reference, the main drive 140 will be referred to as a pulley140 a. Although the pulley 140 a of this embodiment is stationary, inother embodiments, the pulley 140 a could be rotating. The connectionmechanism 150 may be integral with the pulley 140 a or coupled to thepulley 140 a, for example, with mechanical fasteners. As shown in FIG.9A, in one embodiment, the connection mechanism 150 includes, relativeto the pulley 140 a, an outwardly facing portion 150 a and an inwardlyfacing portion 150 b. The outwardly facing portion 150 a forms a portionof a circumferential perimeter 141 of the pulley 140 a and provides anaccess interface for the cables. For example, for each cable 131, 132,133, 134, the connection mechanism 150 includes a coupling member 152configured to receive a distal end of the cable. The coupling member 152may have any configuration suitable for securely anchoring the cable. Inone embodiment, the distal end of the cable has a connector 4 (such as astainless steel or brass ball as shown in FIG. 34) swaged thereto, andthe coupling member 152 includes an angled spherical pocket 153 (orgroove) for receiving and securely seating the connector 4 when thecable is under tension. As long as sufficient tension is maintained onthe cable, the connector 4 remains seated. The cable can be decoupledfrom the coupling member 152 by releasing sufficient tension from thecable. In a preferred embodiment (shown in FIG. 9B), the coupling member152 includes a single pocket 153 for securing the distal end of thecable. Alternatively, the coupling member 153 may be configured tosecure a tension element in at least a first location and a secondlocation. For example, the coupling member may include multiple pockets153, 155 (shown in FIG. 9A) to enable the end of the cable to be securedin a first location or a second location depending, for example, on thelength of the cable.

The connection mechanism 150 preferably includes one or more slotsconfigured to receive the coupling members 152. For example, as shown inFIG. 9B, the connection mechanism 150 includes a first slot 156 a and asecond slot 156 b. The coupling members 152 received in the first slot156 a secure the first set of cables (i.e., the cables 131, 132) whichextend in a first direction (i.e., the direction E) from an upperportion of the connection mechanism 150, and the coupling members 152received in the second slot 156 b secure the second set of cables (i.e.,the cables 133, 134) which extend in a second direction (i.e., thedirection F) from a lower portion of the connection mechanism 150. Thefirst and second slots 156 a, 156 b are preferably offset from oneanother by a predetermined angle α (based, for example, on a diameter ofthe pulley 140 a so that the incoming cables are appropriately orientedin the directions E, F. For example, in the embodiment of FIGS. 9A and9B, the predetermined angle is about 110 degrees. Thus, the firstdirection is offset from the second direction by the predetermined angleα. Once a coupling member 152 is inserted into a slot 156 a, 156 b, thecoupling member 152 can be moved within the slot 156 a, 156 b to adesired location and then fixed in the slot 156 a, 156 b using anysuitable mechanism. In an exemplary embodiment, the coupling member 152is fixed in the slot 156 a, 156 b using a threaded rod 157 that alsofunctions as an adjustment member for adjusting the connection mechanism150 to vary a tension force applied to the flexible transmission 103.For example, as shown in FIG. 9B, the coupling member 152 is connectedto one end of the threaded rod 157, and the other end of the threadedrod 157 includes a tension nut 158, a lock nut 159, and an optionalspacer 151 that extend into the interior of the pulley 140 a. Thus, theadjustment member is disposed at least partially inwardly of thecircumferential perimeter 141 of the pulley 140 a. After the distal endof the cable is seated in the coupling member 152, a tension force isapplied to the cable by tightening the tension nut 158 until the cabletension reaches a desired value. The lock nut 159 is then tightened toprevent the tension nut 158 from loosening over time (e.g., due tovibration). Tightening or loosening the tension nut 158 adjusts thecable tension accordingly. The optional spacer 151 is useful forpositioning the tension and lock nuts 158, 159 so they are easilyaccessible by manufacturing and service personnel. In this manner, theconnection mechanism 150 is configured to be adjusted to vary a tensionforce applied to the flexible transmission 103. In particular, theconnection mechanism 150 is configured to be adjusted to independentlyvary a tension force applied to each of the plurality of tensionelements (i.e., the cables 131, 132, 133, 134). Advantageously, thecoupling member 152 is configured to inhibit rotation of the coupledcable when the connection mechanism 150 is adjusted to vary the tensionforce applied to the flexible transmission 103. In particular, becausethe coupling member 152 is constrained in the slot 156 a, 156 b, thecoupling member 152 will not rotate, and thus prevents rotation of thecable, when the tension nut 158 is adjusted to vary the tension forceapplied to the cable.

The connection mechanism 150 may also include a guide member configuredto position the distal ends of the cables of a cable set in a desiredmanner. In particular, the guide member maintains proper leads of thecables from the connection mechanism 150 back to the pinion 116. Forexample, as shown in FIG. 8B, a guide member 190 a gathers the cables131, 132 of the first cable set together a short distance from where thecables 131, 132 exit the connection mechanism 150. Preferably, the guidemember 190 a gathers the cables 131, 132 at a position where the distalends of the cables 131, 132 are appropriately aligned with the proximalends of the cables 131, 132 leading off the pinion 116. The connectionmechanism 150 can also include a second guide member 190 b to similarlygather and guide the cables 133, 134 of the second cable set. Inparticular, it is desirable to position the distal ends of the cables sothe proximal ends of the cables coming off the pinion 116 maintain asubstantially square or perpendicular relationship to the pinion 116 toavoid unwanted effects, such as grinding. In one embodiment, forexample, the guide member 190 a is configured to maintain a portion ofthe cable 131 (i.e., the first transmission sub-element) substantiallyparallel to a portion of the cable 132 (i.e., the second transmissionsub-element), as shown in FIG. 8B, so the distal end of one (or both) ofthe cables 131, 132 does not pull the proximal end of that cable in anunwanted direction. Similarly, the second guide member 190 b can beconfigured to maintain a portion of the cable 133 (i.e., the thirdtransmission sub-element) substantially parallel to a portion of thecable 134 (i.e., the fourth transmission sub-element). The guide members190 a, 190 b may be any device suitable for guiding the cables. In theembodiment of FIG. 8B, the each guide member 190 a, 190 b includes athreaded pin removably fastened to the connection mechanism 150. Toavoid chafing the cables, the guide members 190 a, 190 b can beconfigured such that there is substantially no relative motion betweenthe guide member 190 a, 190 b and the associated cables in response tomovement of the drive member 110. This can be accomplished, for example,by disposing the guide members 190 a, 190 b remotely from the drivemember 110. For example, as shown in FIG. 8B, the guide members 190 a,190 b can be disposed directly on the connection mechanism 150 in closeproximity to the point where the cables engage the coupling members 152.

Second Joint Assembly

FIGS. 5A to 5E show the second joint assembly 200 according to anembodiment of the invention. The second joint assembly 200 is disposedon the joint output (i.e., the riser assembly 142) of the first jointassembly 100 and thus moves with the joint output of the first jointassembly 100. The second joint assembly 200 includes a first component201, a second component 202, and an at least partially flexibletransmission 203. In this embodiment, the first component 201 includes adrive member 210, and the second component 202 includes a driven member220. The flexible transmission 203 is coupled to the drive member 210and the driven member 220 and is configured to move the driven member220 in response to motion of the drive member 210.

The flexible transmission 203 of the second joint assembly 200 issimilar to the flexible transmission 103 of the first joint assembly 100and includes first and second transmission elements that comprise firstand second cable sets, respectively. The first cable set includes afirst cable 231 and a second cable 232, and the second cable setincludes a third cable 233 and a fourth cable 234. Thus, the secondjoint assembly 200 includes redundant cables the advantages of which aredescribed above in connection with the first joint assembly 100. Forexample, the cables 231, 232 are redundant because each cable 231, 232performs the same function of exerting a tension force on the drivenmember 220 in a direction G (shown in FIG. 5C) when a pinion 216 of thedrive member 210 rotates to wind the cables 231, 232 onto the pinion216. Similarly, the cables 233, 234 are redundant because each cable233, 234 performs the same function of exerting a tension force on thedriven member 220 in a direction H when the pinion 216 rotates to windthe cables 233, 234 onto the pinion 216. In this manner the firsttension element (e.g., the cables 231, 232) is configured to causemovement of the driven member 220 in a first direction (e.g., thedirection G) in response to a first movement of the drive member 210,and the second tension element (e.g., the cables 233, 234) is configuredto cause movement of the driven member 220 in a second direction (e.g.,the direction H) in response to a second movement of the drive member210. The cables 231, 232, 233, 234 may be any cables appropriate for usein a robotic system but are preferably tungsten cables. Although thecables 231, 232, 233, 234 can be configured in a variety of ways toimpart motion to the driven member 220, in this embodiment, each of thecables 231, 232, 233, 234 has a proximal end connected to the drivemember 210 (i.e., the first component 201) and a distal end connected tothe driven member 220 (i.e., the second component 202).

According to an embodiment, the driven member 220 of the second jointassembly 200 is coupled to the joint output of the first joint assembly100, and rotation of the driven member 220 is driven by the drive member210 via the cables 231, 232, 233, 234. For example, as shown in FIG. 5A,supports 240 are rigidly attached to the riser assembly 142 and includebearings that support a main shaft 241. The main shaft 241 is the jointoutput of the second joint assembly 200 and is coupled to (or integralwith) the driven member 220. For example, the driven member 220 isrigidly attached to the main shaft 241 using mechanical fasteners (e.g.,screws) and is also pinned to provide a secondary form of attachment tomitigate the risk of the mechanical fasteners becoming loose. The drivenmember 220 is configured to rotate about an axis I-I in a pendulum-typemotion, which results in rotation of the main shaft 241.

The drive member 210 includes a drive motor 212 that provides motiveforce to the driven member 220. The drive motor 212 may be any motorsuitable for driving the driven member 220. Preferably, the drive motor212 of the second joint assembly 200 is similar to the drive motor 112of the first joint assembly 100 in all aspects, including the pinion,motor encoder, and motor brake, the advantages of which are describedabove in connection with the first joint assembly 100. As shown in FIG.5A, the drive motor 212 is mounted to the riser assembly 142 and/or toone of the supports 240. Each of the cables 231, 232, 233, 234 has aproximal end connected to and wound around the pinion 216 in a manneridentical to that described above in connection with the pinion 116 ofthe first joint assembly 100. As best seen in FIGS. 5C and 5E, the firstand second cable sets extend from the pinion 216 in opposite directions,travel along an underside of the driven member 220, and then curve upand around the driven member 220 before terminating at a connectionmechanism that includes two coupling components 252. A first tensionelement (e.g., the cables 231, 232) is coupled to one coupling component252, and a second tension element (e.g., the cables 233, 234) is coupledto the other coupling component 252. When the drive motor 212 isactuated, the pinion 216 rotates causing the first cable set to windaround (or unwind from) the pinion 216 and the second cable set toconversely unwind from (or wind around) the pinion 216 depending on thedirection of rotation. Because the distal ends of the cables 231, 232,233, 234 are connected to the driven member 220, the winding andunwinding of the cables 231, 232, 233, 234 exerts force and/or torque onthe driven member 220 that causes the driven member 220 (and thus themain shaft 241) to rotate thereby providing the second rotational degreeof freedom J2 shown in FIG. 2. In this manner, the first and secondtransmission elements are configured to cause movement of the drivenmember 220 (i.e., the second component 202) in response to movement ofthe drive member 210.

To limit rotation of the driven member 220, end stop assemblies 242 aredisposed on the support 240 and corresponding stop members 244 aredisposed on the driven member 220. When rotation of the driven member220 causes a stop member 244 to contact its corresponding end stopassembly 242, rotation of the driven member 220 is constrained.Preferably, the end stop assemblies 242 include shock absorbing features(e.g., shock absorbers, rubber mounts, or the like) and are adjustablein both length and angular orientation to enable the end stop assemblies242 to be arranged in a desired alignment relative to the driven member220 and to be adjusted.

To enable rotation of the main shaft 241 with low friction, bearings 243that support the main shaft on the supports 240 are preferably duplexball bearing pairs (shown in FIG. 10). The duplex ball bearing pairs aredesigned such that when the inner races of the duplex pair are pressedtogether axially with a preload force, the axial and radial play of thebearings 243 are removed. In the embodiment of FIG. 10, the inner racesof each duplex ball bearing pair are mounted on a precision groundoutside diameter of the main shaft 241 with a shoulder machined into themain shaft 241 to locate the duplex ball bearing pair axially on themain shaft 241. Threads on the outer ends of the main shaft 241 acceptbearing preload nuts 245 that are tightened until the inner races of theduplex ball bearing pair are pressed together, preloading the bearings243 to eliminate play while maintaining low rotational friction of themain shaft 241.

Preferably, the joint output (in this case, the main shaft 241) includesa joint encoder configured to measure angular rotation of the jointoutput. Any suitable encoder system can be used. In one embodiment, thejoint encoder includes an encoder scale 260 that rotates with the mainshaft 241 and an encoder read head 262 that reads the encoder scale 260.As shown in FIG. 5D, the encoder scale 260 is rigidly attached to an endof the main shaft 241 (e.g., using mechanical fasteners, adhesive,and/or the like), and the encoder read head 262 is fixedly mounted tothe support 240 via a bracket 261 so as to have a line of sight to theencoder scale 260. The bracket 261 is configured to position the encoderread head 262 correctly relative to the encoder scale 260. As the mainshaft 241 rotates, markings on the encoder scale 260 are read by theencoder read head 262 to determine angular position of the main shaft241. For relative encoder systems, an encoder index mark (as describedabove in connection with the joint encoder of the first joint assembly110) is also included. Preferably, the joint encoder is at leastpartially enclosed by a protective cover 263 (shown in FIG. 5B).Advantageously, the joint encoder enables rotational output of the jointoutput to be measured. As discussed above in connection with the firstjoint assembly 100, the rotational output can be compared to therotational input from the drive motor 212 (measured by the motorencoder) to determine whether the integrity of the flexible transmissionhas been compromised.

As shown in FIGS. 5C and 5E, the first and second cable sets of thesecond joint assembly 200 extend from the pinion 216 in oppositedirections and connect to the driven member 220 at the connectionmechanism, which includes the coupling components 252. The couplingcomponents 252 may be integral with or coupled to the driven member 220and may have any configuration suitable for securely anchoring thecables. In one embodiment, the connection mechanism includes first andsecond coupling components (i.e., the two coupling components 252),where the second coupling component is disposed remotely from the firstcoupling component, as seen in FIG. 5C. In this embodiment, eachcoupling component 252 includes a machined block that is attached to thedriven member 220 using one or more fasteners. The distal end of eachcable 231, 232, 233, 234 includes a connector adapted to engage athreaded rod 257, and the machined block includes a through hole (foreach cable) that receives the threaded rod 257. The threaded rod 257 isinserted into the appropriate through hole and secured in the machinedblock using a tension nut 258 and a lock nut 259 in a manner identicalto that described above in connection with the connection mechanism 150of the first joint assembly 100.

In an exemplary embodiment, the connection mechanism (i.e., the couplingcomponents 252) also functions as an adjustment member for varying atension force applied to each cable. For example, a tension force isapplied to a cable by tightening the associated tension nut 258 untilthe cable tension reaches a desired value in a manner identical to thatdescribed above in connection with the connection mechanism 150. Thus,the connection mechanism is a tensioning mechanism disposed on thedriven member 220 (i.e., the second component 202) and configured toapply a tension force to the first transmission element (e.g., thecables 231, 232) and the second transmission element (e.g., the cables233, 234) and to be adjusted to vary the tension force. Because thetensioning mechanism is located on the driven member 220 and thus moveswith the driven member 220, it is referred to as a “floating” tensioner.In contrast, conventional cable tensioners are typically fixed to astationary component. One advantage of using a floating tensioner is amore compact design. Additionally, a floating tensioner enables the useof shorter cables, which can result in a stiffer drive mechanism.

Third Joint Assembly

FIGS. 5A to 5E show the third joint assembly 300 according to anembodiment of the invention. The third joint assembly 300 is disposed onthe joint output (i.e., the main shaft 241) of the second joint assembly200 and thus moves with the joint output of the second joint assembly200. The third joint assembly 300 includes a first component 301, asecond component 302, and an at least partially flexible transmission303. In this embodiment, the first component 301 includes a drive member310, and the second component 302 includes a driven member 320. Theflexible transmission 303 is coupled to the drive member 310 and thedriven member 320 and is configured to move the driven member 320 inresponse to movement of the drive member 310.

The flexible transmission 303 of the third joint assembly 300 is similarto the flexible transmission 103 of the first joint assembly 100 andincludes first and second transmission elements that comprise first andsecond cable sets, respectively. The first cable set includes a firstcable 331 and a second cable 332, and the second cable set includes athird cable 333 and a fourth cable 334. Thus, the third joint assembly300 includes redundant cables the advantages of which are describedabove in connection with the first joint assembly 100. For example, thecables 331, 332 are redundant because each cable 331, 332 performs thesame function of exerting a tension force on the driven member 320 in adirection J (shown in FIG. 11) when a pinion 316 of the drive member 310rotates to wind the cables 331, 332 onto the pinion 316. Similarly, thecables 333, 334 are redundant because each cable 333, 334 performs thesame function of exerting a tension force on the driven member 320 in adirection K when the pinion 316 rotates to wind the cables 333, 334 ontothe pinion 316. In this manner, a first tension element (e.g., thecables 331, 332) is configured to cause movement of the driven member320 in a first direction (e.g., the direction J) in response to a firstmovement of the drive member 310, and a second tension element (e.g.,the cables 333, 334) is configured to cause movement of the drivenmember 320 in a second direction (e.g., the direction K) in response toa second movement of the drive member 310. The cables 331, 332, 333, 334may be any cables appropriate for use in a robotic system but arepreferably tungsten cables. Although the cables 331, 332, 333, 334 canbe configured in a variety of ways to impart motion to the driven member320, in this embodiment, each of the cables 331, 332, 333, 334 has aproximal end connected to the drive member 310 and a distal endconnected to the driven member 320.

According to an embodiment, the driven member 310 of the third jointassembly 300 is coupled to the joint output of the second joint assembly200 (i.e., the main shaft 241), and rotation of the driven member 320 isdriven by the drive member 310 via the cables 331, 332, 333, 334. Forexample, as shown in FIG. 10, an output shaft 341 of the third jointassembly 300 intersects and is disposed on the main shaft 241 of thesecond joint assembly 200 supported by bearings 343. The output shaft341 is the joint output of the third joint assembly 300 and is coupledto (or integral with) the driven member 320. For example, in anexemplary embodiment, the driven member 320 is a pulley 342 that slidesonto the output shaft 341 and is fixedly secured to the output shaft 341by a clamp ring or collar. The pulley 342 (i.e., the driven member 320)is connected to the flexible transmission 303. When actuated by thedrive member 310, the flexible transmission 303 causes the pulley 342,and thus the output shaft 341, to rotate.

The drive member 310 includes a drive motor 312 that provides motiveforce to the driven member 320. The drive motor 312 may be any motorsuitable for driving the driven member 320. Preferably, the drive motor312 of the third joint assembly 300 is similar the drive motor 112 ofthe first joint assembly 100, including the pinion and motor encoder,the advantages of which are described above in connection with the firstjoint assembly 100. The drive motor 312 is mounted on the main shaft241. Each of the cables 331, 332, 333, 334 has a proximal end connectedto and wound around the pinion 316 in a manner identical to thatdescribed above in connection with the pinion 116 of the first jointassembly 100. The first and second cable sets extend from the pinion 316in opposite directions, travel around a portion of a circumference ofthe pulley 342, and terminate at a connection mechanism 350 disposed onthe pulley 342. As shown in FIG. 11, the first and second cable setsengage the connection mechanism 350 on opposite sides. When the drivemotor 312 is actuated, the pinion 316 rotates causing the first cableset to wind around (or unwind from) the pinion 316 and the second cableset to conversely unwind from (or wind around) the pinion 316 dependingon the direction of rotation. Because the distal ends of the cables areconnected to the pulley 342, the winding and unwinding of the cables331, 332, 333, 334 exerts force and/or torque on the pulley 342 thatcauses the pulley 342 (and thus the output shaft 341) to rotate therebyproviding the third rotational degree of freedom J3 shown in FIG. 2.

To limit rotation of the pulley 342, a bumpstop assembly 344 is disposedon the pulley 342 and stop members 346 are disposed on a counterbalanceweight 347 that is mounted on the main shaft 341 (e.g., to counteractthe weight of the joint assemblies 400, 500, 600). When rotation of thepulley 342 causes the bumpstop assembly 344 to contact a stop member346, rotation of the pulley 342 (and thus the output shaft 341) isconstrained.

To enable rotation of the output shaft 341 with low friction, thebearings 343 that support the output shaft 341 on the main shaft 241 arepreferably duplex ball bearing pairs like those discussed above inconnection with the main shaft 241 of the second joint assembly 200. Theduplex ball bearing pairs are mounted in a similar fashion to thebearings 243 except the distance between the duplex ball bearing pairsis controlled by a spacer 348 that functions to translate preload forceimparted by a bearing preload nut 345 to both duplex ball bearing pairs.

One difference between third joint assembly 300 and the first and secondjoint assemblies 100, 200 is that the drive motor 312 of the third jointassembly 300 does not include a motor brake. Instead, the third jointassembly 300 utilizes a joint brake 385 coupled directly to the jointoutput (i.e., the output shaft 341). The joint brake 385 may be anysuitable brake assembly. In one embodiment, the joint brake 385 includesa stator that is connected to the counterbalance weight 347 and a rotorthat is attached to the output shaft 341. The joint brake 385 can beactuated to constrain rotation of the output shaft 341 as appropriate,such as when a fault condition is triggered.

Preferably, the joint output (in this case, the output shaft 341)includes a joint encoder configured to measure angular rotation of thejoint output. Any suitable encoder system can be used. In oneembodiment, the joint encoder is disposed behind the joint brake 385 andis similar to the joint encoder of the second joint assembly 200 exceptan encoder scale (not shown) is attached to the output shaft 341 and anencoder read head (not shown) is attached to the main shaft 241. As theoutput shaft 341 rotates relative to the main shaft 241, the encoderread head reads the encoder scale. Advantageously, the joint encoderenables rotational output of the joint output to be measured. Asdiscussed above in connection with the first joint assembly 100, therotational output can be compared to the rotational input from the drivemotor 312 (measured by the motor encoder) to determine whether theintegrity of the flexible transmission has been compromised.

As noted above, the first and second cable sets of the third jointassembly 300 extend from the pinion 316 in opposite directions andconnect to the pulley 342 (i.e., the driven member 320) at theconnection mechanism 350. As best shown in FIG. 11, when connected, thecables 331, 332 (i.e., a first tension element) extend from a first sideof the connection mechanism 350, and the cables 333, 334 (i.e., a secondtension element) extend from a second side of the connection mechanism350. The connection mechanism 350 may be integral with the pulley 342 orcoupled to the pulley 342 (e.g., with mechanical fasteners) and may haveany configuration suitable for securely anchoring the cables. In anexemplary embodiment, the connection mechanism 350 includes a machinedblock that is attached to the pulley 342 using one or more fasteners. Inthis embodiment, the distal end of each cable includes a connectoradapted to engage a threaded rod 357, and the machined block includes athrough hole (for each cable) that receives the threaded rod 357. Thethreaded rod 357 is inserted into the appropriate through hole andsecured in the machined block using a tension nut 358 and a lock nut 359in a manner identical to that described above in connection with theconnection mechanism 150 of the first joint assembly 100. In anexemplary embodiment, the connection mechanism 350 also functions as anadjustment member for varying a tension force applied to each cable. Forexample, a tension force is applied to a cable by tightening the tensionnut 358 until the cable tension reaches a desired value in the samemanner discussed above in connection with the connection mechanism 150of the first joint assembly 100. In this manner, the connectionmechanism 350 is configured to engage each of the cables 331, 332, 333,334 and is adjustable to vary a tension force applied to each of thecables 331, 332, 333, 334. Additionally, the connection mechanism 350 isa floating tensioner because it moves with the driven member 320.

The connection mechanism 350 may also be used in combination with aguide member that is configured to position the distal ends of thecables of a cable set in a desired manner. In particular, the guidemember maintains proper leads of the cables from the connectionmechanism 350 back around to the pinion 316. In one embodiment, theguide member includes guide members 390 a, 390 b that are identical tothe guide members 190 a, 190 b described above in connection with thefirst joint assembly 100 and function in the same manner.

Fourth Joint Assembly

FIG. 12 shows the second module B according to an embodiment of theinvention. In this embodiment, the second module B includes the fourthjoint assembly 400. As noted above, the fourth joint assembly 400provides one rotational degree of freedom. Thus, the second module Bprovides the fourth degree of freedom of the robotic arm 10. The outputmotion of the second module B is similar to the motion of a human elbowjoint. For this reason, the second module B is also referred to as therobot elbow.

FIGS. 12 and 13 show the fourth joint assembly 400 according to anembodiment of the invention. The fourth joint assembly 400 is disposedon the joint output (i.e., the output shaft 341) of the third jointassembly 300 and thus moves with the joint output of the third jointassembly 300. In contrast to the joint assemblies 100, 200, 300, thefourth joint assembly 400 preferably has a two stage transmission (i.e.,two stages of drive reduction). In one embodiment, the first stage ofthe transmission includes a first component 401 a (which includes adrive member 410 a), a second component 402 a (which includes a drivenmember 420 a), and an at least partially flexible transmission 403 a.Similarly, the second stage of the transmission includes a firstcomponent 401 b (which includes a drive member 410 b), a secondcomponent 402 b (which includes a driven member 420 b), and an at leastpartially flexible transmission 403 b. For the avoidance of confusion,as used in this specification, a drive member is a component used toimpart motion to a driven member and may be (a) “active,” meaningcapable of independent motion (e.g., a drive motor), or (b) “passive,”meaning driven by another component (e.g., a pulley that is driven by amotor). The drive members of the joint assemblies 100, 200, 300preferably are active drive members. In contrast, the fourth jointassembly 400 preferably includes both active and passive drive members.

As shown in FIGS. 12-16, the fourth joint assembly 400 incorporates afirst stage transmission and a second stage transmission. The firststage transmission includes the drive member 410 a that drives thedriven member 420 a via the flexible transmission 403 a. Similarly, thesecond stage transmission includes the drive member 410 b that drivesthe driven member 420 b via the flexible transmission 403 b. As can beseen in FIG. 13, the first and second stage transmissions share acomponent in common. Specifically, the driven member 420 a and the drivemember 410 b are the same component. Because the drive member 410 aimparts motion to the drive member 410 b, the drive member 410 b is apassive drive member as defined above.

According to an embodiment, the drive member 410 a is a drive motor 412(i.e., an active drive member) having a first stage pinion 416 a and thedriven member 420 a is a pulley assembly 442 having a second stagepinion 416 b. The flexible transmission 403 a includes a plurality ofcables that are connected to the drive motor 412 (via the first stagepinion 416 a) and the pulley assembly 442 and transmit force and/ortorque from the drive motor 412 to the pulley assembly 442. As can beseen in FIG. 13, the pulley assembly 442 is also the drive member 410 b(i.e., a passive drive member). The flexible transmission 403 b includesa plurality of cables that are connected to the pulley assembly 442 (viathe second stage pinion 416 b) and the driven member 420 b and transmitforce and/or torque from the pulley assembly 442 to the driven member420 b. The driven member 420 b is an output member 422, which is thejoint output of the fourth joint assembly 400. The second stagetransmission also incorporates an idler pulley 424, which is anon-driven pulley included, for example, to reduce the amount ofunsupported cable in the second stage transmission, which enables thedrive member 410 b to be located remotely from the driven member 420 b.

The first and second stage transmissions of the fourth joint assembly400 are disposed on a rigid frame 425 having a proximal end with anattachment flange 426 that is mounted on the output shaft 341 of thethird joint assembly 300 (e.g., using mechanical fasteners). The rigidframe 425 supports the mechanisms of the drive train and has a lengthsufficient to ensure that the fourth joint assembly 400 provides theappropriate range of motion and “reach” needed by the surgeon tomanipulate the robotic arm 10 to access the relevant portions of thepatient's anatomy. The rigid frame 425 can be made of a rigid material,such as aluminum, a composite (e.g., a Kevlar® composite), or the like.Structural covers 427 can be mounted to the rigid frame 425 to provideadditional stiffness to resist bending and/or torsion caused, forexample, by forces applied by the surgeon as the surgeon manipulates theend effector 700. Preferably, the structural covers 427 include accessopenings 427 a to facilitate inspection of the first and secondtransmissions and permit adjustment of cable tension and encoder systemcomponents without having to remove the structural covers 427. Theability to inspect and adjust joint assembly mechanisms without removingthe structural covers 427 is particularly advantageous because theprocess of removing and reinstalling the structural covers 427 can alterthe overall geometry of the robotic arm 10, such as by altering theoverall flatness and location of a joint assembly's output (e.g., adistal end of the joint assembly) relative to the joint assembly's input(e.g., a proximal end of the joint assembly). Such alteration wouldadversely impact the accuracy of the robotic arm 10, requiringrecalibration to restore accuracy. Calibration is a time consumingprocedure that involves, for example, kinematically calibrating therobotic arm 10 by placing the robotic arm 10 in various known relativepositions, capturing data at each position, comparing measured versusknown position data, and reducing the error therebetween using a bestfit process. Because kinematic calibration takes approximately thirtyminutes, it is desirable to make every effort not to disturb thestructural elements of the joint assemblies during service andinspection. The use of the access openings 427 a in the structuralcovers 427 advantageously enables service and adjustment withoutdisturbing the overall geometry of the robotic arm 10.

The flexible transmissions 403 a, 403 b of the fourth joint assembly 400are similar to the flexible transmission 103 of the first joint assembly100. Each flexible transmission 403 a, 403 b includes tension elements(e.g., cables) and may optionally include redundant tension elements. Inone embodiment, the flexible transmission 403 b includes redundanttension elements while the flexible transmission 403 a is non-redundant.For example, in this embodiment, the flexible transmission 403 aincludes a first transmission element comprising a first cable 431 a anda second transmission element comprising a second cable 432 a. Althoughthe cables 431 a, 432 a can be configured in a variety of ways to impartmotion to the pulley assembly 442, in this embodiment, each of thecables 431 a, 432 a has a proximal end connected to the drive motor 412and a distal end connected to a connection mechanism on the pulleyassembly 442. The cables 431 a, 432 a are not redundant because eachcable performs a different function. Specifically, the cable 431 afunctions to exert a tension force on the pulley assembly 442 in adirection L (shown in FIG. 14A) when the pinion 416 a of the drive motor412 rotates to wind the cable 431 a onto the pinion 416 a. In contrast,the cable 432 a functions to exert a tension force on the pulleyassembly 442 in a direction M when the pinion 416 a rotates to wind thecable 432 a onto the pinion 416 a. In this manner, the flexibletransmission 403 a is coupled to the drive member 410 a and the drivenmember 420 a and is configured to cause movement of the driven member420 a in response to movement of the drive member 410 a. As explainedabove, the flexible transmission 403 a utilizes two cables that are notredundant in function. In contrast, the flexible transmission 403 bincludes a first transmission element having a first plurality oftension elements (or transmission sub-elements) and a secondtransmission element having a second plurality of tension elements (ortransmission sub-elements). In this embodiment, the first transmissionelement is a first cable set that includes the first plurality oftension elements, which includes a first cable 431 b and a second cable432 b. Similarly, the second transmission element is a second cable setthat includes the second plurality of tension elements, which includes athird cable 433 b and a fourth cable 434 b. Thus, the flexibletransmission 403 b includes redundant cables the advantages of which aredescribed above in connection with the first joint assembly 100. Forexample, the cables 431 b, 432 b are redundant because each cable 431 b,432 b performs the same function of exerting a tension force on theoutput member 422 in a direction N (shown in FIG. 14) when the pinion416 b of the pulley assembly 442 rotates to wind the cables 431 b, 432 bonto the pinion 416 b. Similarly, the cables 433 b, 434 b are redundantbecause each cable 433 b, 434 b performs the same function of exerting atension force on the output member 422 in a direction P when the pinion416 b of the pulley assembly 442 rotates to wind the cables 433 b, 434 bonto the pinion 416 b. Although the cables 431 b, 432 b, 433 b, 434 bcan be configured in a variety of ways to impart motion to the outputmember 422, in this embodiment, each of the cables 431 b, 432 b, 433 b,434 b has a proximal end connected to the pulley assembly 442 and adistal end connected to the output member 422. The cables 431 a, 432 a,431 b, 432 b, 433 b, 434 b may be any cables appropriate for use in arobotic system but are preferably tungsten cables.

One potential disadvantage of using a cable transmission is the need topre-tension the cables to eliminate slack that would cause backlash ofthe transmission. Pre-tensioning load values are typically 15% to 50% ofthe cable breaking strength, which results in large cable tension forcesbeing imparted to bearings of drive train components and their supportstructure. For example, as shown in FIG. 14C, the simplest cablearrangement is one where each cable leads off one side of a drive traincomponent Q (e.g., a drive member) and leads onto the next drive traincomponent R (e.g., a driven member) on the same side. The resultantcable force Tr is the sum of a cable tension force T1 and a cabletension force T2, and the bending moment Mb is the resultant cable forceTr times a distance D1 from the cables to a neutral axis of the supportstructure (e.g., the rigid frame 425). As illustrated by the length ofthe arrow in FIG. 14D, for this simple cable arrangement, the resultantcable force Tr has a large magnitude, which results in large bearingloads and bending moments. The high load also increases friction forcesin the drive train components and contributes to surgeon fatiguebecause, to manipulate the robotic arm 10, the surgeon must applysufficient force to overcome the increased friction forces.

According to an embodiment, the cables of the first and second stagetransmissions are preferably configured to reduce loads on drive traincomponent bearings and bending moments on the rigid frame 425. One wayto decrease the loads and moments is to arrange the cables in a mannerthat decreases the resultant cable force Tr. In one embodiment, this isaccomplished by arranging the cables in a “crossover” (or “tangentwrap”) configuration where the cables overlap one another between drivetrain components. In other words, the cables are crossed at eachjuncture between drive train components. For example, as shown in FIG.14A, the cables of the first stage transmission are arranged so thecable 431 a crosses over (or under) the cable 432 a after the cables 431a, 432 a lead off the drive motor 412 but before they contact the pulleyassembly 442. The cables of the second stage transmission are similarlyarranged. Thus, for both the first and second stage transmissions, thefirst transmission element crosses the second transmission element atleast once between the coupling of the first transmission element to thedrive member 410 a, 410 b and the coupling of the first transmissionelement to the driven member 420 a, 420 b. Another way to describe thecrossover configuration (using the second stage transmission in FIG. 14Ato illustrate) is to consider a plane S defined by an axis of rotation Uof the drive member 410 b and an axis of rotation V of the driven member420 b (or an intermediate component, such as the idler pulley 424). Theaxes of rotation U, V are parallel. As can be seen, the first and secondtransmission elements of the second stage transmission each include aportion in contact with the drive member 410 a, a portion in contactwith at least one of the driven member 420 b and the intermediatecomponent (e.g., the idler pulley 424), and a portion therebetween,where the portion therebetween intersects the plane S. Because thecables 431 b, 432 b and the cables 433 b, 434 b are oriented to overlapone another in this manner, the tension forces of the cables 431 b, 432b, 433 b, 434 b partially offset one another so the resultant cableforce Tr is less than the sum of a tension force T1 of the cables 431 b,432 b and a tension force T2 of the cables 433 b, 434 b. As illustratedin FIG. 14B, this results in a lower resultant cable force Tr than thatshown in FIG. 14D, which advantageously reduces bearing loads andbending moments.

Motive force is provided to the fourth joint assembly 400 by the drivemember 410 a. As noted above, the drive member 410 a includes the drivemotor 412, which imparts rotational motion to the pulley assembly 442via the flexible transmission 403 a. The drive motor 412 may be anymotor suitable for driving the pulley assembly 442. In one embodiment,the drive motor 412 is integral with the rigid frame 425. The integralconstruction includes a stator bonded directly to the rigid frame 425and a rotor 419 having a motor shaft 414 from which the first stagepinion 416 a extends. Integral construction advantageously increasesstructural strength of the rigid frame 425 while creating a compactdesign for the fourth joint assembly 400. Additionally, integralconstruction improves drive motor cooling because the rigid frame 425 isa substantial heat sink, and thermal conduction is greater with anintegral stator than with a separate stator that is bolted to the rigidframe 425.

Preferably, the drive motor 412 includes a motor encoder configured tomeasure angular rotation of the motor shaft 414. The motor encoder maybe similar to the encoder measurement systems discussed above inconnection with the drive motors of the joint assemblies 100, 200, 300.For example, as shown in FIG. 13, the motor encoder includes an encoderscale (not shown) that rotates with the motor shaft 414 and an encoderread head 462 a that reads the encoder scale. Thus, the motor encoderenables measurement of the angular rotation of the motor shaft 414,which, as discussed above in connection with the joint assembly 100 canbe compared with the angular rotation of the joint output (e.g., asmeasured by a joint encoder) to evaluate the integrity of the flexibletransmission of the fourth joint assembly 400. Additionally, the drivemotor 412 may optionally include a motor brake similar to the motorbrake 111 described above in connection with the first joint assembly100.

As shown in FIG. 17, the motor shaft 414 of the drive motor 412 isbonded to the rotor 419, and the first stage pinion 416 a extends fromthe motor shaft 414. The first stage pinion 416 a may be coupled to orintegral with the motor shaft 414 and includes attachment elements 470for securing the proximal ends of the cables 431 a, 432 a. An attachmentelement 470 may have any configuration suitable for securely anchoring acable to the pinion 416 a. For example, the attachment element 470 maybe similar to the attachment elements 170 described above in connectionwith pinion 116 of the first joint assembly 100. Alternatively, in oneembodiment, the proximal end of each cable 431 a, 432 a has a connector4 (such as a stainless steel or brass ball as shown in FIG. 34) swagedthereto, and the attachment element 470 is configured to seat theconnector 4 when the cable is under tension. For example, as shown inFIG. 17, the attachment element 470 comprises a rounded (e.g.,hemispherical) groove 474 (or relief) sized to receive the connector 4and a channel groove 473 large enough to receive the cable but not topermit the connector 4 to pass from the rounded groove 474 to thechannel groove 473. When the connector 4 is fitted into the roundedgroove 474, the cable is seated in the channel groove 473, and tensionis applied to the cable in a direction away from the connector 4, theconnector 4 seats into the rounded groove 474. As long as sufficienttension is maintained on the cable, the connector 4 remains seated. Thecable can be decoupled from the attachment element 470 by releasingsufficient tension from the cable.

Preferably, one attachment element 470 is disposed on each end of thepinion 416 a. The cable 431 a engages the attachment element 470 on adistal end of the pinion 416 a, and the cable 432 a engages theattachment element 470 on a proximal end of the pinion 416 a. For eachattachment element 470, the portion of the cable that exits theattachment element 470 engages a guide 480. The guide 480 may be similarto the guide 180 described above in connection with the first jointassembly 100 except, in this embodiment, the guide 480 is configured foruse with single cables as opposed to redundant cables. For example,instead of a double helix arrangement, the guide 480 may be a singlespiral (e.g., helical) groove (or “single helix” arrangement) thatextends along a length of the first stage pinion 416 a. The guide 480receives the cables 431 a, 432 a, which wind around the first stagepinion 416 a in opposite directions and eventually lead off the firststage pinion 416 a and wrap circumferentially around the pulley assembly442 in opposite directions before terminating at a connection mechanismdisposed on the pulley assembly 442.

The connection mechanism may be integral with or coupled to the pulleyassembly 442 and may have any configuration suitable for securelyanchoring the cables 431 a, 432 a. For example, the connection mechanismmay be similar to one or more of the connection mechanisms describedabove in connection with the joint assemblies 100, 200, 300. In theembodiment of FIG. 18, the connection mechanism includes a firstcoupling component 452 a and a second coupling component 452 b disposedremotely from the first coupling component 452 a. In this embodiment,each coupling component 452 a, 452 b is disposed inwardly of acircumferential perimeter 442 a of the pulley assembly 442 and includesa base 453 that is attached to the pulley assembly 442 with mechanicalfasteners. The pulley assembly 442 includes apertures 442 b throughwhich the cables 431 a, 432 a pass to reach the coupling components 452a, 452 b. Each coupling component 452 a, 452 b includes a couplingmember 454 configured to receive a distal end of a cable and a slot 455configured to receive the coupling member 454. The coupling member 454and slot 455 are preferably similar to the coupling member 152 and slots156 a, 156 b described above in connection with the first joint assembly100, including incorporating a threaded rod 457, tension nut 458, andlock nut 459 that function as an adjustment member for varying a tensionforce applied to the cable.

Rotation of the pulley assembly 442 occurs when the drive motor 412actuates causing the first stage pinion 416 a to rotate. When the firststage pinion 416 a rotates, the cable 431 a winds around (or unwindsfrom) the pinion 416 a and the cable 432 a conversely unwinds from (orwinds around) the pinion 416 a depending on the direction of rotation.Because the distal ends of the cables 431 a, 432 a are coupled to thepulley assembly 442, the winding and unwinding of the cables 431 a, 432a exerts force and/or torque on the pulley assembly 442 that causes thepulley assembly 442 to rotate. As explained above, the pulley assembly442 is a passive drive member that imparts rotational motion to theoutput member 422 via the flexible transmission 403 b. In particular,the pulley assembly 442 includes the second stage pinion 416 b to whichproximal ends of the cables 431 b, 432 b, 433 b, 434 b are coupled. Whenthe pulley assembly 442 rotates, the cables 431 b, 432 b wind around (orunwind from) the second stage pinion 416 b and the cables 433 b, 434 bconversely unwind from (or wind around) the second stage pinion 416 bdepending on the direction of rotation. Because the distal ends of thecables 431 b, 432 b, 433 b, 434 b are coupled to the output member 422,the winding and unwinding of the cables 431 b, 432 b, 433 b, 434 bexerts force and/or torque on the output member 422 that causes theoutput member 422 to rotate thereby providing the fourth rotationaldegree of freedom J4 shown in FIG. 2.

The pulley assembly 442 preferably includes a pulley brake 411configured to inhibit rotation of the second stage pinion 416 b. Thepulley brake 411 may be any suitable brake assembly but is preferably apermanent magnet type brake manufactured by Kendrion ElectromagneticGroup of Germany. The brake 411 is internal to the pulley assembly 442.For example, as shown in FIG. 20, the pulley assembly 442 includes apulley 460 that is rigidly attached to a shaft 461 of the second stagepinion 416 b with a collar type shaft clamp 462. The shaft 461 ismounted to the rigid frame 425 via a cross roller bearing 464. The brake411 includes a brake hub 466 that is fixed to an internal portion of thepulley 460 and a brake body 463 that is fixed to the rigid frame 425. Inoperation, when the brake 411 is energized, the brake hub 462 (and thuspulley 460, shaft clamp 462, and second stage pinion 416 b) is free torotate relative to the rigid frame 425. When power is removed from thebrake 411, however, the brake 411 constrains the brake hub 462, whichinhibits rotation of the pulley 460, shaft clamp 462, and second stagepinion 416 b. Similar to the motor brake 111 discussed above inconnection with the first joint assembly 100, the pulley brake 411 is afailsafe mechanism that can be triggered, for example, in response to afault signal. Additionally, as described above in connection with thefirst joint assembly 100, the incorporation of a brake on the secondstage drive member (i.e., the pulley assembly 442) along with redundantcables in the second stage flexible transmission 403 b, enables thejoint output (i.e., the output member 422) to be unbraked.

The second stage pinion 416 b includes attachment elements for securingthe proximal ends of the cables 331 b, 332 b, 333 b, 334 b. Anattachment element may have any configuration suitable for securelyanchoring a cable to the pinion 416 b. For example, the attachmentelement may be similar to the attachment elements 170 described above inconnection with the first joint assembly 100. Alternatively, in oneembodiment, the second stage pinion 416 b includes attachment elementsthat are similar to the attachment elements 470 of the first stagepinion 416 a, and the proximal end of each of the cables 431 b, 432 b,433 b, 434 b includes a connector 4 (such as stainless steal or brassballs as shown in FIG. 34) swaged thereto that seats in an attachmentelement in the same manner described above in connection with the firststage pinion 416 a. In contrast to the first stage pinion 416 a (whichincludes two attachment elements 470 for two cables), the second stagepinion 416 b includes four attachment elements 470 a, 470 b, 470 c, 470c (shown in FIG. 19A) disposed along a length of the second stage pinion416 b to accommodate the four cables 431 b, 432 b, 433 b, 434 b. Asshown in FIG. 19B, the cables 431 b, 432 b couple to the attachmentelements 470 a, 470 b, respectively, and the cables 433 b, 434 b coupleto the attachment elements 470 c, 470 d, respectively. For eachattachment element 470 a, 470 b, 470 c, 470 d, the portion of the cablethat exits the attachment element engages a guide. The guide may besimilar to the guide 480 described above in connection with the firststage pinion 416 a except the guide is configured for use with redundantcables as opposed to single cables. For example, in this embodiment, theguide includes a first guide 480 a that receives and guides the cable431 b and a second guide 480 b that receives and guides the cable 434 b.The guide also includes a third guide 480 c disposed between the firstand second guides 480 a, 480 b that receives and guides the cables 432b, 433 b. In particular, the cable 432 b is received in a proximalportion of the third guide 480 c, and the cable 333 b is received in adistal portion of the third guide 480 c. Each of the first, second, andthird guides 480 a, 480 b, 480 c comprises a single spiral (e.g.,helical) groove (or “single helix” arrangement) that extends along aportion of the length of the second stage pinion 416 b. Alternatively,the second stage pinion 416 b could incorporate a double helixarrangement as described above in connection with the pinion 116 of thefirst joint assembly 100. As shown in FIGS. 14A and 19B, the cables 331b, 332 b and the cables 333 b, 334 b wind around the second stage pinion416 b in opposite directions, lead off the second stage pinion 416 b andwrap circumferentially around the idler pulley 424, lead off the idlerpulley 424 and are routed onto a proximal curved end of the outputmember 422, and terminate at connection mechanisms disposed on theoutput member 422.

The idler pulley 424 is a non-driven pulley included, for example, toreduce the amount of unsupported cable in the second stage transmission.Although this embodiment includes one idler pulley, other embodimentsmay include multiple idler pulleys or no idler pulleys. Whether toinclude an idler pulley(s) can be determined based on, for example,transmission configuration details, such as the distance between thedrive member and the driven member. The idler pulley 424 may be anypulley known in the art for supporting a tension element in a tensionelement drive transmission. Advantageously, the combined use of idlerpulleys and the crossover cable configuration enables transmission ofpower over a distance while minimizing drive friction and structuralloading due to cable tension, which allows the design of a flexibletransmission that is backdrivable with extremely low backlash.

The output member 422, which is driven by the pulley assembly 442 viathe flexible transmission 403 b, is the joint output for the fourthjoint assembly 400. As shown in FIGS. 15 and 16, in one embodiment, theoutput member 422 is a plate-like component having a curved proximal endonto which the cables 431 b, 432 b, 433 b, 434 b wrap. The output member422 is coupled to the rigid frame 425 via a cross roller bearing 465.The cross roller bearing 465 may be any suitable cross roller bearingthat can maintain stiffness of the elbow joint while keeping frictionlow. In a preferred embodiment, the cross roller bearing 465 ismanufactured by IKO Nippon Thompson Co., Ltd. of Japan. As shown in FIG.21, an inner race 465 a of the cross roller bearing 465 is coupled tothe rigid frame 425 with mechanical fasteners, and an outer race 465 bof the cross roller bearing 465 is coupled to the output member 422 withmechanical fasteners. The output member 422 may also provide points ofattachment for the protective covers 20 and/or the bellows 22 as well asmounting posts for the protective cover 20 for the fifth joint assembly500.

As with the joint assemblies 100, 200, 300, the joint output (in thiscase the output member 422) of the fourth joint assembly 400 preferablyincludes a joint encoder configured to measure angular rotation of thejoint output. Any suitable encoder system can be used. In oneembodiment, as shown in FIG. 21, the joint encoder includes an encoderscale 468 a mounted to the inner race 465 a of the cross roller bearing465 through a spacer and an encoder read head 468 b (shown in FIGS. 15and 16) coupled to the output member 422. As the output member rotates,markings on the encoder scale 468 a are read by the encoder read head468 b to determine angular position of the output member 422. Forrelative encoder systems, an encoder index mark is also included asdiscussed above in connection with the joint encoder of the first jointassembly 100. As explained above, the rotational output can be comparedto the rotational input from the drive motor 412 (measured by the motorencoder) to determine whether the integrity of the flexible transmissionhas been compromised.

As shown in FIGS. 15 and 16, the output member includes a firstconnection mechanism 450 a for securing the cables 331 b, 332 b and asecond connection mechanism 450 b for securing the cables 333 b, 334 b.The first and second connection mechanisms 450 a, 450 b may be integralwith or coupled to the output member 422 and may have any configurationsuitable for securely anchoring the cables 431 b, 432 b, 433 b, 434 b.According to an embodiment, the first and second connection mechanisms450 a, 450 b comprise brackets 451 a, 451 b, respectively, that aremounted on the output member 422 using mechanical fasteners. Eachbracket 451 a, 451 b includes two through holes for receiving therespective cables. In this embodiment, the distal end of each cableincludes a threaded rod 457 that is inserted into the correspondingthrough hole and secured using a tension nut 458 and a lock nut 459 in amanner identical to that described above in connection with the couplingcomponents 252 of the second joint assembly 200. In an exemplaryembodiment, the threaded rod 457, tension nut 458, and lock nut 459 alsofunction as an adjustment member for varying a tension force applied toeach cable 431 b, 432 b, 433 b, 434 b as described above in connectionwith the coupling components 252 of the second joint assembly 200.

Fifth Joint Assembly

FIG. 22A shows the third module C according to an embodiment of theinvention. In this embodiment, the third module C includes the fifthjoint assembly 500. As noted above, the fifth joint assembly 500provides one rotational degree of freedom. Thus, the third module Cprovides the fifth degree of freedom of the robotic arm 10. The outputmotion of the third module C is similar to the rotation of a humanforearm.

FIGS. 22A-22D show the fifth joint assembly 500 according to anembodiment of the invention. The fifth joint assembly 500 is disposed onthe joint output (i.e., the output member 422) of the fourth jointassembly 400 and thus moves with the joint output of the fourth jointassembly 400. The fifth joint assembly 500 includes a first component501, a second component 502, and an at least partially flexibletransmission 503. In this embodiment, the first component 501 includes adrive member 510, and the second component 502 includes a driven member520. The flexible transmission 503 is coupled to the drive member 510and the driven member 520 and is configured to move the driven member520 in response to movement of the drive member 510.

According to an embodiment, the fifth joint assembly 500 includes asupport structure comprising front and back plates 540, 541 separated byspacers 542 and a lateral plate 543. This support structure supports thedrive member 510 and the driven member 520 and provides points ofattachment for attaching the fifth joint assembly 500 (e.g., usingmechanical fasters) to the output member 422 of the fourth jointassembly 400, as shown in FIG. 4. The front and back plates 540, 541also support brackets 545, which provide mounting locations for theprotective covers 20. In this embodiment, the drive member 510 is adrive motor 512 (i.e., an active drive member), and the driven member520 is an output pulley 522 disposed on an output shaft 524 that issupported on angular contact bearings 523. The bearings 523 are axiallypreloaded using a bearing preload nut 521 to remove axial and radialplay that could contribute to errors in positioning of the end effector700. The flexible transmission 503 includes a plurality of cables thatare connected to the drive motor 512 and the output pulley 522 andtransmit force and/or torque from the drive motor 512 to the outputpulley 522. The output pulley 522 is the joint output of the fifth jointassembly 500. To limit rotation of the output pulley 522, a hard stop525 is disposed on the front plate 540 and corresponding hard stopbumpers (not shown) are disposed on the output pulley 522. When rotationof the output pulley 522 causes a hard stop bumper to contact the hardstop 525, rotation of the output pulley 522 is constrained.

The drive member 510 provides motive force to the fifth joint assembly500. As noted above, the drive member 510 includes the drive motor 512,which imparts rotational motion to the output pulley 522 via theflexible transmission 503. The drive motor 512 may be any motor suitablefor driving the output pulley 522. As shown in FIG. 23, the drive motor512 includes a housing 517 that houses a rotor 519 and a stator 518 thatturn a motor shaft 514. As with the joint assemblies 100, 200, 300, 400,the drive motor 512 includes a motor encoder to enable measurement ofthe angular rotation of the motor shaft 514. In this embodiment, themotor encoder includes an encoder scale 560 that rotates with the motorshaft 514 and an encoder read head 562 mounted to the housing 517 thatreads the encoder scale 560. Similarly, the joint output (in this case,the output pulley 522) includes a joint encoder configured to measureangular rotation of the joint output. In one embodiment, the jointencoder includes an encoder scale 563 (shown in FIG. 22B) attached tothe output shaft 524 via a locking nut and an encoder read head 564(shown in FIG. 22A) attached to the back plate 541 via a bracket. As theoutput shaft 524 (and thus the output pulley 522) rotates relative tothe back plate 541, the encoder read head 564 reads the encoder scale563. As a result, the angular rotational input provided by the drivemotor 512 (measured by the motor encoder) can be compared to the angularrotational output of the joint output (measured by the joint encoder) todetermine whether the integrity of the flexible transmission of thefifth joint assembly 500 has been compromised.

The fifth joint assembly 500 is similar to the third joint assembly 300in that the drive motor 512 does not include a motor brake. Instead, thefifth joint assembly 500 utilizes a joint brake 511 coupled directly tothe joint output (i.e., the output pulley 522). The joint brake 511 maybe any suitable brake assembly. In one embodiment, the joint brake 511is coupled to the output pulley 522 via the output shaft 524. Forexample, the joint brake 511 includes a rotor that is rigidly attachedto the output shaft 524 using a brake shaft clamp. The joint brake 511can be actuated to constrain rotation of the output shaft 524 (and thusthe output pulley 522) as appropriate, such as when a fault condition istriggered or if loss of power occurs. Inclusion of the joint brake 511in the fifth joint assembly 500 means that non-redundant cables can beused in the flexible transmission 503 without compromising the safety ofthe robotic arm 10.

As shown in FIG. 23, the drive motor shaft 514 includes a pinion 516 towhich the flexible transmission 503 is coupled. According to anembodiment, the flexible transmission 503 of the fifth joint assembly500 is similar to the flexible transmission 403 a of the first stagetransmission of the fourth joint assembly 400 and includes a pluralityof tension elements. Although the flexible transmission 503 mayoptionally include redundant tension elements, in this embodiment,incorporation of the joint brake 511 enables the use of non-redundanttension elements, as noted above. In this embodiment, the flexibletransmission 503 is non-redundant and includes a first transmissionelement comprising a first cable 531 (i.e., a first tension element) anda second transmission element comprising a second cable 532 (i.e., asecond tension element). Although the cables 531, 532 can be configuredin a variety of ways to impart motion to the output pulley 522, in thisembodiment, each of the cables 531, 532 has a proximal end connected tothe drive motor 512 (i.e., at the pinion 516) and a distal end connectedto the output pulley 522. The cables 531, 532 are not redundant becauseeach cable 531, 532 performs a different function. Specifically, thecable 531 functions to exert a tension force on the output pulley 522 ina direction W (shown in FIG. 22C) when the pinion 516 rotates to windthe cable 531 onto the pinion 516. In contrast, the cable 532 functionsto exert a tension force on the output pulley 522 in a direction X whenthe pinion 516 rotates to wind the cable 532 onto the pinion 516. Thus,the flexible transmission 503 utilizes two cables that are not redundantin function. The cables 531, 532 may be any cables appropriate for usein a robotic system but are preferably tungsten cables.

As shown in FIG. 24, the pinion 516 includes attachment elements 570 forsecuring the proximal ends of the cables 531, 532. An attachment element570 may have any configuration suitable for securely anchoring a cableto the pinion 516. For example, an attachment element 570 may be similarto any of the attachment elements described herein, such as theattachment elements described in connection with the joint assemblies100, 400. In one embodiment, the proximal end of each cable 531, 532 hasa connector 4 (such as a stainless steel or brass ball as shown in FIG.34) swaged thereto, and the attachment element 570 is configured to seatthe connector 4 when the cable is under tension in the same manner asdescribed above in connection with the attachment elements of the fourthjoint assembly 400. The pinion 516 includes two attachment elements 570(one for the cable 531 and one for the cable 532) disposed on oppositeends of the pinion 516. As shown in FIG. 22C, each cable 531, 532 has aproximal end connected to and wound around the pinion 516 in the samemanner as described above in connection with the pinion 116 of the firstjoint assembly 100. The first and second cables 531, 532 lead off (orextend from) the pinion 516 in opposite directions. Although both cables531, 532 could be routed directly from the pinion 516 to the drivenmember 520 (e.g., as described above in connection with the pinion 416 aof the fourth joint assembly 400), in this embodiment, the cable 531leads off the pinion 516 and loops around an adjustment member 570(e.g., a tensioner assembly) located above the pinion 516, then travelsdownward past the pinion 516 and wraps around a circumferentialperimeter of the output pulley 522, and finally terminates at aconnection mechanism 550 on the output pulley 522. Thus, as best shownin FIG. 22C, the flexible transmission 503 includes a first tensionelement (i.e., the cable 531) having a first (or proximal) portion 531 acoupled to the drive member 510 (i.e., the pinion 516), a second (ordistal) portion 531 b coupled to the driven member 520, and anintermediate portion 531 c between the first portion 531 a and thesecond portion 531 b, where the adjustment member 570 engages theintermediate portion 531 c. In contrast, the second tension element(i.e., the cable 532) is not engaged by the adjustment member 570.Instead, the cable 532 includes a portion coupled to the drive member510 and a portion coupled to the driven member 520. The cable 532 leadsoff the pinion 516, travels downward and wraps around the circumferenceof the output pulley 522, and then terminates at the connectionmechanism 550 on the output pulley 522. The cables 531, 532 engage theconnection mechanism 550 from opposite sides. When the drive motor 512is actuated, the pinion 516 rotates causing the cable 531 to wind around(or unwind from) the pinion 516 and the cable 532 to conversely unwindfrom (or wind around) the pinion 516 depending on the direction ofrotation. Because the distal ends of the cables 531, 532 are connectedto the output pulley 522, the winding and unwinding of the cables 531,532 exerts force and/or torque on the output pulley 522 that causes theoutput pulley 522 to rotate thereby providing the fifth rotationaldegree of freedom J5 shown in FIG. 2.

The drive member 510 is disposed between the driven member 510 and theadjustment member 570. The adjustment member 570 is configured to beadjusted to vary a tension force applied to at least one of the cables531, 532. Unlike conventional cable tensioning devices, the adjustmentmember 570 is not coupled to an end of the cable to be tensioned.Instead, the adjustment member 70 is configured to engage theintermediate portion 531 c of the cable, which is a part of the cablelocated between the proximal and distal ends. Although the adjustmentmember 570 can be designed to engage the cable 531, the cable 532, orboth of the cables 531, 532, in a preferred embodiment, the adjustmentmember 570 engages only the cable 531. In operation, movement of theadjustment member 570 toward or away from the pinion 516 varies thetension force applied to the intermediate portion 531 c (and thus to thecable 531 overall). Because (1) the cables 531, 532 are both coupled tothe pinion 516 and the output pulley 522 and (2) the output pulley 522is able to rotate, adjustment of the tension force applied to the cable531 automatically results in adjustment of the tension force applied tothe cable 532 in accordance with principles of equilibrium. Thus, theflexible transmission 503 is configured so that a tension force appliedto the second tension element (i.e., the cable 532) is varied when theadjustment member 570 is adjusted to vary the tension force applied tothe first tension element (i.e., the cable 531). As a result, the twoseparate cables 531, 532 of the fifth joint assembly 500 can both betensioned by adjusting only one tensioning mechanism (i.e., theadjustment member 570). In contrast, conventional cable tension devicesmay require adjustment of two separate tensioning mechanisms to adjustthe tension of two separate cables. Alternative embodiments includeengaging both cables 531, 532 with the adjustment member 570 orincluding an independent adjustment member for each cable 531, 532.

As will be recognized by one of skill in the art, the adjustment member570 can have any configuration that (a) is capable of engaging theintermediate portion of at least one of the cables 531, 532 and (b) isadjustable to vary a tension force applied thereto. The configuration ofthe adjustment member 570 can be determined based on various factors,such as the size of the joint assembly and the amount of space availablefor travel of the adjustment member 570. According to one embodiment, asshown in FIGS. 22B and 26, an adjustment member 570 a includes a supportbracket 571 a coupled to the front plate 540 and a yoke 572 a coupled tothe support bracket 571 a by a tension adjustment screw 573 a. Thetension adjustment screw 573 a is held in position by a tension nut 558and a lock nut 559. The yoke 572 a is also coupled directly to the frontplate 540 via fasteners 574 a that engage corresponding elongated slots575 a in the yoke 571 a. A portion of the adjustment member 570 acomprises a tension pulley 576 a that is supported in the yoke 571 a bybearings. In the installed configuration, the cable 531 leads off thepinion 516 and loops around the tension pulley 576 a, then travelsdownward past the pinion 516 and wraps around a circumference of theoutput pulley 522 before being secured to the connection mechanism 550on the output pulley 522. The portion of the cable 531 that loops overthe tension pulley 576 a is the intermediate portion 531 c. To tensionthe cable 531, the fasteners 574 a are loosened, which enables the yoke571 a (and thus the tension pulley 576 a) to move relative to the frontplate 540 along a linear path. The tension nut 558 is then tightened,which draws up the tension adjustment screw 573 a. The yoke 571 a iscoupled to the tension adjustment screw 573 a and therefore travelsupward as the tension adjustment screw 573 a is drawn up in a directionY. The tension pulley 576 a moves upward with the yoke 571 a, therebyincreasing a tension force applied to the cable 531. To decrease thetension force, the tension nut 558 is loosened, which moves the yoke 571a and tension pulley 576 a downward in a direction Z. In this manner,the adjustment member 570 a is configured to increase a tension forceapplied to the first tension element (i.e., the cable 531) when theadjustment member 570 a moves in a first direction (i.e., the directionY) and to decrease a tension force applied to the first tension elementwhen the adjustment member 570 a moves in a second direction (i.e., thedirection Z). In this embodiment, the first and second directions arealong a line (or a predetermined axis A-A). When the cable 531 istensioned to a desired value, the lock nut 559 is tightened to preventloosening of the tension nut 558 (e.g., due to vibration). The fasteners574 a are also tightened to constrain the yoke 571 a relative to thefront plate 540. As explained above, tensioning the cable 531 in thismanner advantageously also results in tensioning of the cable 532.

According to another embodiment, as shown in FIGS. 27A and 27B, anadjustment member 570 b is configured to travel along a nonlinear path(e.g., an arcuate path) to tension a cable. A nonlinear path may bedesirable, for example, in situations where a joint assembly does nothave sufficient space for an adjustment member to travel linearly. Inthis embodiment, the adjustment member 570 b is similar to theadjustment member 570 a except the adjustment member 570 b is configuredto rotate about a pivot line B-B (or a predetermined axis), whichresults in a tensioner pulley 576 b moving along an arc. For example,the adjustment member 570 b includes a yoke 572 b that is coupled to thefront plate 540 with a first fastener 574 b that defines the pivot lineB-B and a second fastener 574 c that engages an elongated slot 575 b inthe yoke 572 b. When the fasteners 574 b, 574 c are tightened, the yoke572 b is constrained relative to the front plate 540. When the fasteners574 b, 574 c are loosened, the yoke 572 b is permitted to rotate aboutthe pivot line B-B. The adjustment member 570 b also includes a supportbracket 571 b that supports a tension adjustment screw 573 b. Thetension adjustment screw 573 b is coupled to a threaded pin 577 b thatis pivotably coupled to the yoke 572 b. The yoke 572 b further includesbearings that support the tension pulley 576 b. In the installedconfiguration (which is identical to the installed configuration of theadjustment member 570 a), the cable 531 leads off the pinion 516 andloops around the tension pulley 576 b, then travels downward past thepinion 516 and wraps around the circumference of the output pulley 522before being secured to the connection mechanism 550 on the outputpulley 522. To tension the cable 531, the fasteners 574 b, 574 c areloosened, and the tension adjustment screw 573 b is adjusted (e.g.,using a hex wrench engaged with a recess 578 b in the tension adjustmentscrew 573 b, which causes the yoke 572 b to pivot about the pivot lineB-B. For example, turning the tension adjustment screw 573 b so that theyoke 572 b pivots in a clockwise direction about the pivot line B-Bcauses the tension pulley 576 b disposed on the yoke 572 b to moveupward in a first direction DD along a slight arc, thereby increasing atension force exerted on the cable 531. To decrease the tension force,the tension adjustment screw 573 b is turned so that the yoke 572 bpivots in a counterclockwise direction about the pivot line B-B, whichcauses the tension pulley 576 b to move downward in a direction EEthereby decreasing a tension force exerted on the cable 531. In thisembodiment, the first and second directions DD, EE are along an arc.When the cable 531 is tensioned to a desired value, the fasteners 574 b,574 c are tightened to constrain the yoke 572 b relative to the frontplate 540. As explained above, tensioning the cable 531 in this manneradvantageously also results in tensioning of the cable 532.

As shown in FIGS. 22A-C, the output pulley 522 includes the connectionmechanism 550 for securing the cables 531, 532. The connection 550 mayhave any configuration suitable for securing the cables 531, 532. Forexample, the connection mechanism 550 could be similar to any of theconnection mechanisms described herein. Additionally, in lieu of theadjustment member 570, the connection mechanism 550 could be configuredto be adjustable to vary the tension force applied to each cable 531,532. In one embodiment, the connection mechanism 550 is formedintegrally with the output pulley 522. For example, the connectionmechanism 550 comprises a slot 551 formed in the circumferentialperimeter of the output pulley 522. The slot 551 includes an opening 552that is large enough to receive a connector 4 (such as a stainless steelor brass ball as shown in FIG. 34) that is coupled to the distal end ofeach of the cables 531, 532. The slot 551 also includes a projection 553a adapted to restrain the connector 4 of one of the cables 531, 532 whenthe connector 4 is inserted into the opening 552 and tension is exertedon the cable in a direction away from the connector 4. Similarly, theslot 551 includes a projection 553 b adapted to restrain the connector 4of the other cable 531, 532 when the connector 4 is inserted into theopening 552 and tension is exerted on the cable in a direction away fromthe connector 4. As long as sufficient tension is maintained on a cable,the connector 4 is retained by the connection mechanism 550, as shown inFIG. 25C. A cable can be decoupled from the connection mechanism 550 byreleasing tension from the cable. In this manner, the connectionmechanism 550 is configured to removably secure the cables 531, 532 tothe output pulley 522.

Sixth Joint Assembly

FIGS. 28A-28E show the fourth module D according to an embodiment of theinvention. In this embodiment, the fourth module D includes the sixthjoint assembly 600. As noted above, the sixth joint assembly 600provides one rotational degree of freedom. Thus, the fourth module Dprovides the sixth degree of freedom of the robotic arm 10. The outputmotion of the fourth module D is similar to the motion of a human wristjoint. For this reason, the fourth module D is also referred to as therobot wrist.

FIGS. 28A-28E show the sixth joint assembly 600 according to anembodiment of the invention. The sixth joint assembly 600 is disposed onthe joint output (i.e., the output pulley 522) of the fifth jointassembly 500 (as shown in FIG. 4) and thus moves with the joint outputof the fifth joint assembly 500. Like the fourth joint assembly 400, thesixth joint assembly 600 has a two stage transmission. In oneembodiment, the first stage of the transmission includes a firstcomponent 601 a (which includes a drive member 610 a), a secondcomponent 602 a (which includes a driven member 620 a), and an at leastpartially flexible transmission 603 a. Similarly, the second stage ofthe transmission includes a first component 601 b (which includes adrive member 610 b), a second component 602 b (which includes a drivenmember 620 b), and an at least partially flexible transmission 603 b. Aswith in the fourth joint assembly 400, the sixth joint assembly 600includes both active and passive drive members.

As shown in FIG. 28E, the six joint assembly 600 incorporates a firststage transmission and a second stage transmission. The first stagetransmission includes the drive member 610 a that drives the drivenmember 620 a via the flexible transmission 603 a. Similarly, the secondstage transmission includes the drive member 610 b that drives thedriven member 620 b via the flexible transmission 603 b. As can be seen,the first and second stage transmissions share a component in common.Specifically, the driven member 620 a and the drive member 610 b are thesame component. Because the drive member 610 a imparts motion to thedrive member 610 b, the drive member 610 b is a passive drive member asdefined above.

According to an embodiment, the drive member 610 a is a drive motor 612(i.e., an active drive member) having a first stage pinion 616 a, andthe driven member 620 a is an intermediate pulley assembly 642 having asecond stage pinion 616 b. The flexible transmission 603 a includes aplurality of cables that are connected to the first stage pinion 616 aand the intermediate pulley assembly 642 and transmit force and/ortorque from the drive motor 612 to the intermediate pulley assembly 642.As can be seen in FIG. 28A, the intermediate pulley assembly 642 is alsothe drive member 610 b (i.e., a passive drive member). The flexibletransmission 603 b includes a plurality of cables that are connected tothe second stage pinion 616 b and the driven member 620 b and transmitforce and/or torque from the intermediate pulley assembly 642 to thedriven member 620 b. The driven member 620 b is an output pulleyassembly 622, which is the joint output of the sixth joint assembly 600.The second stage transmission also incorporates multiple idler pulleys624, which are non-driven pulleys included, for example, to reduce theamount of unsupported cable in the second stage transmission, minimizeradial loads on the bearings that support drive train components, andminimize bending moments on a rigid frame 625 that supports the drivetrain components. As shown in FIG. 28B, the cables of the second stagetransmission are routed in a serpentine fashion around the idler pulleys624. The drive reduction of the first stage transmission is the ratio ofthe diameter of the intermediate pulley assembly 642 to the diameter ofthe first stage pinion 616 a. This drive reduction causes the rotationangle of the intermediate pulley assembly 642 to be less than therotational angle of the first stage pinion 616 a by the inverse of thevalue of the drive reduction and also causes the torque transmittedbetween the drive motor 612 and the intermediate pulley assembly 642 tobe higher by the ratio of the drive reduction. Similarly, the drivereduction of the second stage transmission is the ratio of the diameterof the output pulley assembly 622 to the diameter of the second stagepinion 616 b. The total drive reduction of the sixth joint assembly 600is the drive reduction of the first stage transmission multiplied by thedrive reduction of the second stage transmission.

The first and second stage transmissions of the sixth joint assembly 600are disposed on the rigid frame 625 having a proximal end with anattachment flange 626 that is mounted on the output pulley 522 of thefifth joint assembly 500 (e.g., using mechanical fasteners). The rigidframe 625 supports the drive components and has a length (e.g., from theattachment flange 626 to a center of rotation of the driven member 620b) sufficient to ensure that the sixth joint assembly 600 provides theappropriate range of motion and “reach” needed by the surgeon tomanipulate the robotic arm 10 to access the relevant portions of thepatient's anatomy. The rigid frame 625 can be made of a rigid material,such as aluminum, a composite (e.g., a Kevlar® composite), or the like.Structural covers 627 (shown in FIG. 3) can be mounted to the rigidframe 625 to provide additional stiffness to resist bending and/ortorsion caused, for example, by forces applied by the surgeon as thesurgeon manipulates the end effector 700. Preferably, the structuralcovers 627 include access openings 627 a to facilitate inspection of thefirst and second transmissions and permit adjustment of cable tensionand encoder system components without having to remove the structuralcovers 627.

The flexible transmissions 603 a, 603 b of the sixth joint assembly 600are similar to the flexible transmission 103 of the first joint assembly100. Each flexible transmission 603 a, 603 b includes tension elements(e.g., cables or cords) and may optionally include redundant tensionelements. In one embodiment, the flexible transmission 603 b includesredundant tension elements while the flexible transmission 603 a isnon-redundant. For example, in this embodiment, the flexibletransmission 603 a includes a first transmission element comprising afirst cable 631 a and a second transmission element comprising a secondcable 632 a. Although the cables 631 a, 632 a can be configured in avariety of ways to impart motion to the intermediate pulley assembly642, in this embodiment, each of the cables 631 a, 632 a has a proximalend connected to the drive motor 612 (i.e., at the pinion 616 a) and adistal end connected to the intermediate pulley assembly 642. The cables631 a, 632 a are not redundant because each cable 631 a, 632 a performsa different function. Specifically, the cable 631 a functions to exert atension force on the intermediate pulley assembly 642 in a direction FF(shown in FIG. 28D) when the pinion 616 a rotates to wind the cable 631a onto the pinion 616 a. In contrast, the cable 632 a functions to exerta tension force on the intermediate pulley assembly 642 in a directionGG when the pinion 616 a rotates to wind the cable 632 a onto the pinion616 a. Thus, the flexible transmission 603 a utilizes two cables thatare not redundant in function. In contrast, the flexible transmission603 b includes a first transmission element having a first plurality oftension elements (transmission sub-elements) and a second transmissionelement having a second plurality of tension elements (transmissionsub-elements). In this embodiment, the first transmission element is afirst cable set that includes the first plurality of tension elements,which includes a first cable 631 b and a second cable 632 b. Similarly,the second transmission element is a second cable set that includes thesecond plurality of tension elements, which includes a third cable 633 band a fourth cable 634 b. Thus, the flexible transmission 603 b includesredundant cables the advantages of which are described above inconnection with the first joint assembly 100. For example, the cables631 b, 632 b are redundant because each cable 631 b, 632 b performs thesame function of exerting a tension force on the output pulley assembly622 in a direction HH (shown in FIG. 28B) when the pinion 616 b rotatesto wind the cables 631 b, 632 b onto the pinion 616 b. Similarly, thecables 633 b, 634 b are redundant because each cable 633 b, 634 bperforms the same function of exerting a tension force on the outputpulley assembly 622 in a direction JJ when the pinion 616 b rotates towind the cables 633 b, 634 b onto the pinion 616 b. Although the cables631 b, 632 b, 633 b, 634 b can be configured in a variety of ways toimpart motion to the output pulley assembly 622, in this embodiment,each of the cables 631 b, 632 b, 633 b, 634 b has a proximal endconnected to the intermediate pulley assembly 642 and a distal endconnected to the output pulley assembly 622. The cables 631 a, 632 a,631 b, 632 b, 633 b, 634 b may be any cables appropriate for use in arobotic system but are preferably tungsten cables.

As discussed above in connection with the fourth joint assembly 400, onepotential disadvantage of using a cable transmission is the need topre-tension the cables, which results in large cable tension forcesbeing imparted to the drive train component bearings and their supportstructure. Accordingly, the cables of the first and second stagetransmissions are preferably configured to minimize such loads byutilizing the “crossover” (or “tangent wrap”) configuration describedabove in connection with the fourth joint assembly 400. For example, asshown in FIG. 28D, the cables of the first stage transmission arearranged so the cable 531 a crosses the cable 532 a after the cableslead off the drive motor 612 but before they contact the intermediatepulley assembly 642. As shown in FIG. 28B, the cables 531 b, 532 b, 533b, 534 b of the second stage transmission are similarly arranged.

Motive force is provided to the sixth joint assembly 600 by the drivemember 610 a. As noted above, the drive member 610 a includes the drivemotor 612, which imparts rotational motion to the intermediate pulleyassembly 642 via the flexible transmission 603 a. The drive motor 612may be any motor suitable for driving the intermediate pulley assembly642. In one embodiment, the drive motor 612 is integral with the rigidframe 625 similar to the drive motor 412 of the fourth joint assembly400. In another embodiment, the drive motor 612 is an independentassembly (shown in FIG. 29) that is bolted to the rigid frame 625. Thedrive motor 612 includes a stator 618 along with a rotor 619 that isbonded to a motor shaft 614. Preferably, the drive motor 612 includes amotor encoder configured to measure angular rotation of the motor shaft614. The motor encoder may be similar to the encoder measurement systemsdiscussed above in connection with the drive motors of the other jointassemblies. For example, the motor encoder includes an encoder scale 615a that rotates with the motor shaft 614 and an encoder read head 615 b(mounted on a bracket) that reads the encoder scale 615 a. Thus, themotor encoder enables measurement of the angular rotation of the motorshaft 614, which, as discussed above in connection with the jointassembly 100 can be compared with the angular rotation of the jointoutput (e.g., as measured by a joint encoder) to determine whether theintegrity of the flexible transmission of the sixth joint assembly 600has been compromised. The drive motor 612 may optionally include a motorbrake as described above in connection with the first joint assembly100.

The motor shaft 614 of the drive motor 612 is bonded to the rotor 619,and the first stage pinion 616 a extends from the motor shaft 614. Thefirst stage pinion 616 a may be coupled to or integral with the motorshaft 614 and includes attachment elements 670 for securing the proximalends of the cables 631 a, 632 a. An attachment element 670 may have anyconfiguration suitable for securely anchoring a cable to the pinion 616a. For example, an attachment element 670 may be similar to any of theattachment elements described herein in connection with the other jointassemblies. In one embodiment, the proximal end of each cable 631 a, 632a has a connector 4 (such as a stainless steel or brass ball as shown inFIG. 34) coupled thereto, and the attachment element 670 is configuredto seat the connector 4 when the cable is under tension in the samemanner described above in connection with the attachment elements of thefourth joint assembly 400.

As shown in FIG. 29, the pinion 616 a includes two attachments element670 disposed at approximately a midpoint of the first stage pinion 616a. Each cable 631 a, 632 a has a proximal end connected to an attachmentelement 670 and is wound around the pinion 616 a, as shown in FIG. 28D.For each cable 631 a, 632 a, the portion of the cable that exits theattachment element 670 engages a guide 680 a, 680 b, respectively. Theguides 680 a, 680 b may be similar to the guide described above inconnection with the pinion 416 a of the fourth joint assembly 400 (i.e.,a single spiral groove or “single helix” arrangement). In the embodimentof FIG. 29, the first guide 480 a extends from the attachment element670 along a length of the first stage pinion 616 a toward a proximal endof the pinion 616 a and receives one of the cables 631 a, 632 a.Similarly, the second guide 480 b extends from a different attachmentelement 670 along a length of the first stage pinion 616 a toward adistal end of the pinion 616 a and received the other cable 631 a, 632a. When received in the guides 480 a, 480 b, the cables 631 a, 632 awind around the first stage pinion 616 a in opposite directions andeventually lead off the first stage pinion 616 a and wrapcircumferentially around the intermediate pulley assembly 642 inopposite directions before terminating at a connection mechanismdisposed on the intermediate pulley assembly 642.

The connection mechanism may be integral with or coupled to theintermediate pulley assembly 642 and may have any configuration suitablefor securely anchoring the cables 631 a, 632 a. For example, theconnection mechanism may be similar to one or more of the connectionmechanisms described herein in connection with the other jointassemblies. In one embodiment, the connection mechanism includes anupper coupling component 652 to which the cable 631 a is coupled and alower coupling component (not shown) to which the cable 632 a iscoupled. The upper coupling component 652 is similar to the couplingcomponent on the pulley assembly 442 of the fourth joint assembly 400,including incorporation of a threaded rod, tension nut, and lock nutthat function as an adjustment member (or floating tensioner) forvarying a tension force applied to the cable 631 a. In contrast, thelower coupling component (not shown) includes a grooved portion thatcaptures a connector 4 (such as a stainless steel or brass ball as shownin FIG. 34) on the distal end of the cable 632 a in a manner similar tothe attachment elements of the first stage pinion 616 a. Although thelower coupling component does not have a mechanism for tensioning thecable 632 a, because (a) the cables 631 a, 632 a are both coupled to thefirst stage pinion 616 a and the intermediate pulley assembly 642 and(b) the intermediate pulley assembly 642 is able to rotate, adjustmentof the tension force applied to the cable 631 a automatically results inadjustment of the tension force applied to the cable 632 a in accordancewith principles of equilibrium. As a result, the two separate cables 631a, 632 a of the sixth joint assembly 600 can both be tensioned byadjusting only one tensioning mechanism.

Rotation of the intermediate pulley assembly 642 occurs when the drivemotor 612 actuates causing the first stage pinion 616 a to rotate. Whenthe first stage pinion 616 a rotates, the cable 631 a winds around (orunwinds from) the pinion 616 a and the cable 632 a conversely unwindsfrom (or winds around) the pinion 616 a depending on the direction ofrotation. Because the distal ends of the cables 631 a, 632 a are coupledto the intermediate pulley assembly 642, the winding and unwinding ofthe cables 631 a, 632 a exerts force and/or torque on the intermediatepulley assembly 642 that causes the intermediate pulley assembly 642 torotate. As explained above, the intermediate pulley assembly 642 is apassive drive member that imparts rotational motion to the output pulleyassembly 622 via the flexible transmission 603 b. In particular, theintermediate pulley assembly 642 includes the second stage pinion 616 bto which proximal ends of the cables 631 b, 632 b, 633 b, 634 b arecoupled. When the intermediate pulley assembly 642 rotates, the cables631 b, 632 b wind around (or unwind from) the second stage pinion 616 band the cables 633 b, 634 b conversely unwind from (or wind around) thesecond stage pinion 616 b depending on the direction of rotation.Because the distal ends of the cables 631 b, 632 b, 633 b, 634 b arecoupled to the output pulley assembly 622, the winding and unwinding ofthe cables 631 b, 632 b, 633 b, 634 b exerts force and/or torque on theoutput pulley assembly 622 that causes the output pulley assembly 622 torotate thereby providing the sixth rotational degree of freedom J6 shownin FIG. 2.

The intermediate pulley assembly 642 preferably includes a pulley brake611 configured to inhibit rotation of the second stage pinion 616 b. Thepulley brake 611 may be any suitable brake assembly but is preferably apermanent magnet type brake manufactured by Kendrion ElectromagneticGroup of Germany. The brake 611 is internal to the intermediate pulleyassembly 642 in the same manner as described above in connection withthe pulley brake 411 of the fourth joint assembly 400 (shown in FIG. 20)and operates in the same manner. The pulley brake 611 is a failsafemechanism that can be triggered, for example, in response to a faultsignal. Additionally, as described above in connection with the firstjoint assembly 100, the incorporation of a brake on the second stagedrive member along with redundant cables in the second stage flexibletransmission 603 b, enables the joint output to be unbraked.

The second stage pinion 616 b includes attachment elements for securingthe proximal ends of the cables 631 b, 632 b, 633 b, 634 b. Anattachment element may have any configuration suitable for securelyanchoring a cable to the pinion 616 b. For example, the attachmentelement may be similar to any of the attachment elements describedherein in connection with the other joint assemblies. In one embodiment,the attachment elements are similar to the attachment elements 670 ofthe first stage pinion 616 a, and the proximal ends of the cables 631 b,632 b, 633 b, 634 b include connectors 4 that seat in the attachmentelements in the same manner described above in connection with the firststage pinion 616 a. In contrast to the first stage pinion 616 a (whichincludes two attachment elements 670 for two cables), the second stagepinion 616 b includes four attachment elements 670 a, 670 b, 670 c, 670d disposed along a length of the second stage pinion 616 b toaccommodate the four cables 631 b, 632 b, 633 b, 634 b. As shown in FIG.30, the cables 631 b, 632 b couple to the attachment elements 670 a, 670b, respectively, and the cables 633 b, 634 b couple to the attachmentelements 670 c, 670 d, respectively. For each attachment element, theportion of the cable that exits the attachment element engages a guide.The guide may be similar to the guide described above in connection withthe first stage pinion 616 a except the guide is configured for use withredundant cables as opposed to single cables. For example, in thisembodiment, the guide includes a first guide 680 c that receives andguides the cable 631 b, a second guide 680 d that receives and guidesthe cable 632 b, a third guide 680 e that receives and guides the cable633 b, and a fourth guide 680 f that receives and guides the cable 634b. Each of the guides 680 c, 680 d, 680 e, 680 f comprises a singlespiral (e.g., helical) groove (or “single helix” arrangement) thatextends along a portion of the length of the second stage pinion 616 b.Alternatively, the second stage pinion 616 b could incorporate a doublehelix arrangement as described above in connection with the pinion 116of the first joint assembly 100. As shown in FIG. 28B, the cables 631 b,632 b and the cables 633 b, 634 b wind around the second stage pinion616 b in opposite directions, lead off the second stage pinion 616 b,and wrap circumferentially around a portion of each of the idler pulleys624. The cables 631 b, 632 b, 633 b, 634 b lead off the last idlerpulley 624 and onto the output pulley assembly 622 where the cables 631b, 632 b, 633 b, 634 b terminate at a connection mechanism disposed onthe output pulley assembly 622. The idler pulleys 424 are intermediatecomponents disposed between the drive member 610 b and the driven member620 b. In this manner, the first transmission element (e.g., the cables631 b, 632 b) and the second transmission element (e.g., the cables 633b, 634 b) contact each of a plurality of intermediate components (e.g.,the idler pulleys 424) between the coupling of the first transmissionelement to the drive member 610 b and the coupling of the firsttransmission element to the driven member 620 b.

The idler pulleys 424 are non-driven pulleys included, for example, toreduce the amount of unsupported cable in the second stage transmission.Although this embodiment includes four idler pulleys 424, otherembodiments may include more idler pulleys, fewer idler pulleys, or noidler pulleys. Whether to include an idler pulley(s) can be determinedbased, for example, on transmission configuration details, such as thedistance between the drive member and the driven member. The idlerpulley 424 may be any pulley known in the art for supporting a tensionelement in a tension element drive transmission. Advantageously, thecombined use of idler pulleys and the crossover cable configurationenables transmission of power over a distance while minimizing drivefriction and structural loading due to cable tension, which allows thedesign of a flexible transmission that is backdrivable with extremelylow backlash.

The output pulley assembly 622 is the driven member 620 b of the secondstage transmission and is driven by the intermediate pulley assembly 642via the flexible transmission 603 b. The output pulley assembly 622 isthe joint output for the sixth joint assembly 600. In one embodiment thedriven member 620 b includes a first component and a second componentcoupled to the first component. For example, as shown in FIG. 31A, theoutput pulley assembly 622 includes a first pulley 690 a that isdisposed on and coupled to a second pulley 690 b. The pulleys 690 a, 690b are coupled to the rigid frame 625 via a cross roller bearing 665. Anouter race 665 b of the cross roller bearing 665 is coupled to the rigidframe 625 with mechanical fasteners, and an inner race 665 a of thecross roller bearing 665 is coupled to the output pulley assembly 622with mechanical fasteners. As shown in FIG. 28B, the cables 631 b, 632 bwrap onto the pulley 690 a, and the cables 633 b, 634 b wrap onto thepulley 690 b.

As with the other joint assemblies, the joint output (in this case, theoutput pulley assembly 622) of the sixth joint assembly 600 preferablyincludes a joint encoder configured to measure angular rotation of thejoint output. Any suitable encoder system can be used. In oneembodiment, as shown in FIGS. 31A and 31D, the joint encoder includes anencoder scale 661 a mounted to the inner race 665 a of the cross rollerbearing 665 through a spacer and an encoder read head 661 b coupled tothe rigid frame 625. A protective cover 668 for the encoder scale 661 amay also be utilized. As the output pulley assembly 622 rotates,markings on the encoder scale 661 a are read by the encoder read head661 b to determine angular position of the output pulley assembly 622.For relative encoder systems, an encoder index mark is also included asexplained above in connection with the joint encoder of the first jointassembly 100. Based on data from the joint encoder, the rotationaloutput can be compared to the rotational input from the drive motor 612(measured by the motor encoder) to determine whether the integrity ofthe flexible transmission has been compromised.

As shown in FIGS. 31B and 31C, the output pulley assembly 622 includesfour connection mechanisms 650 for securing each of the cables 631 b,632 b, 633 b, 634 b. The connection mechanisms 650 may be integral withor coupled to the output pulley assembly 622 and may have anyconfiguration suitable for securely anchoring the cables. For example,the connection mechanisms 650 may be similar to one or more of theconnection mechanisms described herein in connection with the otherjoint assemblies. According to an embodiment, two connection mechanisms650 are disposed on the pulley 690 a, and two connection mechanisms 650are disposed on the pulley 690 b. Each connection mechanism 650 islocated inwardly of a circumferential perimeter of the associated pulley690 a, 690 b on which it is disposed and is recessed below a face of theassociated pulley 690 a, 690 b. As best shown in FIG. 31A, the firstcomponent (i.e., the pulley 690 a) and the second component (i.e., thepulley 690 b) enclose at least some of the connection mechanisms 650(e.g., the connection mechanisms 650 disposed on the pulley 690 b). Toenable each recessed connection mechanism 650 to mate with itsrespective cable, the associated pulley 690 a, 690 b includes a recess691 configured to receive a portion of the flexible transmission 603 b(i.e., the cable that mates to the connection mechanism 650). Theconnection mechanisms 650 are preferably similar to the couplingcomponents on the pulley assembly 442 of the fourth joint assembly 400and function in the same manner. For example, each connection mechanism650 includes a coupling member 652 and the associated pulley 690 a, 690b includes a slot 692 (or recess) configured to receive the couplingmember 652. The coupling member 652 and slot 692 are preferably similarto the coupling member and slot described above in connection with theconnection mechanism 150 of the first joint assembly 100, includingincorporating a threaded rod 657 and tension nut 658 that function as anadjustment member (or floating tensioner) for varying a tension forceapplied to the cable. Because each connection mechanism 650 is recessedinto its associated pulley 690 a, 690 b, each tension nut 658 of theoutput pulley assembly 622 is elongated to enable a user to access thetension nut. For example, an elongated portion 658 a of the tension nut658 is received in a channel 693. The channel 693 is configured toenable a user to adjust the connection mechanism 650 to vary the tensionforce applied to the flexible transmission 603 b. For example, as shownin FIG. 31C, the elongated portion 658 a provides access for a user totension the tension nuts. Set screws 659 prevent loosening of thetension nuts 658 (e.g., due to vibration). In this manner, theconnection mechanism is configured to be adjustable without decouplingthe pulley 690 a and the pulley 690 b.

As shown in FIGS. 2 and 3, the end effector 700 of the robotic arm 10attaches to the joint output (i.e., the output pulley assembly 622) ofthe sixth joint assembly 600 via a mounting flange 705 that is rigidlyattached to the output pulley assembly 622 through a cross rollerbearing (not shown). In one embodiment, the mounting flange 705 andmating surface of the end effector 700 form a semi-kinematic coupling asdescribed in U.S. patent application Ser. No. ______, entitled DEVICETHAT CAN BE ASSEMBLED BY COUPLING, filed Dec. 22, 2009 (Attorney DocketNo. 051892-0358), which is hereby incorporated by reference herein inits entirety. The end effector 700 may be any end effector appropriatefor the application for which the robotic arm 10 will be used. In oneembodiment, the end effector is an end effector as described in U.S.patent application Ser. No. ______, entitled END EFFECTOR WITH RELEASEACTUATOR, filed Dec. 22, 2009 (Attorney Docket No. 051892-0351), whichis hereby incorporated by reference herein in its entirety. A surgicaltool 710 (such as a cutting burr) is coupled to the end effector 700. Inoperation, the surgeon grasps and moves the end effector 700 to performa surgical task on a patient, such as cutting bone during a jointreplacement procedure with the surgical tool 710. During the surgicalprocedure, the robotic arm 10 provides haptic feedback (e.g., tactile orforce feedback) to the surgeon to guide the surgeon in performing thesurgical task, as described, for example in U.S. patent application Ser.No. 11/357,197, filed Feb. 21, 2006 (Pub. No. US 2006/0142657), which ishereby incorporated by reference herein in its entirety.

Triple Connector Cable

The flexible transmission embodiments described above in connection withthe joint assemblies 100, 200, 300, 400, 500, 600 utilize cables where acable comprises a length of cable LL with a first connector 4 (such as aswaged ball, threaded rod, or other connection mechanism) disposed on aproximal end LP of the cable LL and a second connector 4 disposed on adistal end LD of the cable LL, as shown in FIG. 34. For ease ofreference, a cable with two connectors may be referred to as a “doubleconnector” cable. The proximal end LP of a double connector cable istypically connected to a drive member and the distal end LD of thedouble connector cable is typically connected to a driven member. In anon-redundant configuration (e.g., the first stage of the sixth jointassembly 600), only two double connector cables are used, i.e., one topull the driven member in one direction and another to pull the drivenmember in another direction. When redundancy is desired (e.g., thesecond stage of the sixth joint assembly 600), two cable sets are usedwhere each cable set includes two double connector cables that areredundant. In other words, the first and second plurality oftransmission sub-elements (i.e., the first and second cable sets) eachinclude at least two cables, where each cable has a first end connectedto the drive member and a second end connected to the second component(in this case, the main drive). One cable set pulls the driven member inone direction, and the other cable set pulls the driven member inanother direction.

Other cable configurations can also be used. For example, in analternative embodiment, a cable includes three connectors, as shown inFIG. 35. For ease of reference, a cable with three connectors may bereferred to as a “triple connector” cable. In this embodiment, thetriple connector cable includes a cable having a first connector 4 adisposed on a proximal end LD of the cable, a second connector 4 bdisposed on a distal end LD of the cable, and a third connector 4 cdisposed between the first and second connectors 4 a, 4 b. This resultsin a triple connector cable having a first cable segment L1 disposedbetween the first and third connectors 4 a, 4 c and a second cablesegment L2 disposed between the second and third connectors. The firstand second cable segments L1, L2 may be part of a continuous length ofcable or may be separate cables.

One advantage of using a triple connector cable is that one tripleconnector cable can replace two double connector cables. Thus, insteadof using two double connector cables to form a plurality of transmissionsub-elements, one triple connector cable can be used. In one embodiment,the plurality of transmission sub-elements can be a triple connectorcable that includes the first and second cable segments L1, L2 connectedto a first component (i.e., a drive member) and to the third connector 4c, where the third connector 4 c is coupled to a second component (e.g.,a driven member). Conversely, a plurality of transmission sub-elementscan be a triple connector cable that includes the first and second cablesegments L1, L2 coupled to the second component (e.g., a driven member)and to the third connector 4 c, where the third connector 4 c is coupledto the first component (i.e., a drive member). For example, asillustrated in FIG. 36A, the third connector 4 c of the triple connectorcable can be engaged with a drive member XX (or a driven member), andthe first and second cable connectors 4 a, 4 b can be engaged with adriven member YY (or a drive member). Engagement can be accomplishedusing any suitable means, such as any of the attachment elements orconnection mechanisms described above in connection with the jointassemblies 100, 200, 300, 400, 500, 600. As shown in FIG. 36A, the firstcable segment L1 pulls the driven member YY in a direction Y1 when thedrive member XX rotates to wind the first cable segment L1 about thedrive member XX, and the second cable segment L2 pulls the driven memberYY in a direction Y2 when the drive member XX rotates to wind the secondcable segment L2 about the drive member XX. In the embodiment of FIG.36A, using one triple connector cable creates a non-redundantconfiguration. Redundancy can be achieved by adding a second triplecable connector.

FIG. 36B shows an alternative embodiment where the first and secondcable segments L1, L2 of the triple connector cable are redundant inthat both the first and second cable segments L1, L2 pull the drivenmember YY in the direction Y1 when the drive member XX rotates to windthe first and second cable segments L1, L2 about the drive member XX. Todrive the driven member YY in the direction Y2, a second tripleconnector cable can be added. As noted parenthetically above, in theembodiments of FIGS. 36A and 36B, the first and second connectors 4 a, 4b can be coupled to one member (e.g., the drive member or the drivenmember), and the third connector 4 c can be coupled to another member(e.g., the driven member or the drive member, respectively).

Another advantage of a triple connector cable is that there is equaltension balance in both the first and second cable segments L1, L2,which may improve haptic stiffness and possibly reduce cable wear.Additionally, the entire triple connector cable can be tensioned using asingle cable tension adjustment member. Thus, in accordance withprinciples of equilibrium, when a triple connector cable is used to formthe plurality of transmission sub-elements and a tension force isapplied to one of the transmission sub-elements (e.g., the first cablesegment L1), an equivalent tension force is applied to another of thetransmission sub-elements (e.g., the second cable segment L2). As aresult, only one of the cable segments L1, L2 needs to be adjusted totension the entire triple connector cable.

Stand Assembly

According to an embodiment, as shown in FIG. 1, the robotic arm 10 isdisposed on a stand assembly 800. As shown in FIG. 32, the standassembly 800 includes a structural frame 802 that mechanically supportsthe robotic arm 10 and provides a mounting area for electronics,computer hardware, and other components associated with the robotic arm10 as well as power and communications electronics for the guidancemodule 2 and camera system 3. The structural frame 802 also providesattachment points for protective covers 805. The robotic arm 10 may besecured to the stand, for example, by affixing the baseplate 144 of thefirst joint assembly 100 to the stand assembly 800 using mechanicalfasteners, such as bolts. The stand assembly 800 preferably includes ahandle 810 and casters 812 to enhance the mobility of the robotic arm 10so that the robotic arm 10 can be easily moved, for example, out of theoperating room after completion of a surgical procedure.

In addition to ease of mobility, the stand assembly 800 is preferablyalso configured to maintain the robotic arm 10 in a stable configurationto minimize global movement during surgery. Any suitable stabilizingmechanism may be used. According to an embodiment, the standincorporates a lift assembly 900 that includes a mobile configuration inwhich the stand assembly 800 is supported on the casters 812 and astationary configuration in which the stand assembly 800 is supported onleg members. In the mobile configuration, the stand assembly 800 caneasily be rolled from one location to another. In the stationaryconfiguration, the stand assembly 800 is substantially immobile.Preferably, the stand assembly 800 is self-leveling in the stationaryconfiguration. For example, the leg members may include three fixedlength leg members 912 a and one self-leveling leg member 912 b. Thethree fixed length leg members 912 a define a plane, and theself-leveling leg member 912 b is compliant to accommodate a floor thatis uneven. In one embodiment, the self-leveling leg member 912 b is aspring loaded leg member (shown in FIG. 33D) that is compliant in thesense that it travels up and down based on the force of a spring 915 andthus can conform to a floor that is uneven. As a result, the standassembly 800 advantageously stabilizes itself automatically and will notwobble even when resting on a floor that is not level. Because the standassembly 800 automatically levels itself, manual leveling of the legmembers 912 a, 912 b is not required. This is particularly advantageousbecause conventional manual leveling adjustment typically requiresadjustment of leg members with a wrench, which means the person carryingout the adjustment has to lay on the floor of the operating room (whichmay not be clean) and manually raise and/or lower feet on the legmembers. This is a time consuming, hazardous process that may have to berepeated each time the stand assembly 800 is moved to a new location. Incontrast, the self-leveling feature enables quick set up of the roboticarm 10 and requires no additional tools for final adjustments.

As shown in FIG. 33A, the lift assembly includes a bottom plate 920 anda top plate 930 that is moveable relative to the bottom plate 920. Thecasters 812 are mounted on the bottom plate 920, and the fixed lengthleg members 912 a, self-leveling leg member 912 b, and structural frame802 of the stand assembly 800 are mounted on the top plate 930. Inoperation, a foot pedal 940 operates a hydraulic pump that actuates ahydraulic cylinder 945. As hydraulic pressure increases, the hydrauliccylinder 945 expands (FIG. 33A), and levers 948 pivot to raise the topplate 930. As a result, the leg members 912 a, 912 b move upward suchthat the stand assembly 800 is supported by the casters 812 in themobile configuration. To transition to the stationary configuration, alift release pedal 949 is depressed, which releases pressure from thehydraulic pump causing the hydraulic cylinder 945 to retract (FIG. 33B),which pivots the levers 948 to lower the top plate 930. As a result, theleg members 912 a, 912 b move downward such that the stand assembly 800is supported by the leg members 912 a, 912 b. A compression spring 944disposed at the base of each leg member 912 a, 912 b assists in raisingthe associated caster 812 to ensure that the leg member 912 a, 912 bmakes contact with the floor. As shown in FIG. 33B, in this embodiment,the leg members 912 a, 912 b are at least partially disposed within thecasters 812 such that each leg member 912 a, 912 b extends through itscorresponding caster 812. One advantage of this configuration is thatthe lift assembly is more compact. Another advantage is that, in themobile configuration, the leg members 912 a, 912 b are retracted withinthe casters 812, which protects the leg members 912 a, 912 b from damagethat might be incurred as the stand assembly 800 is rolled overthresholds or rough, uneven flooring or pavement.

Other embodiments of the present invention will be apparent to thoseskilled in the art from consideration of the specification and practiceof the invention disclosed herein. It is intended that the specificationand examples be considered as exemplary only.

1. A transmission, comprising: a first component having a drive member and a portion configured to be actuated to inhibit movement of the drive member; a second component; and first and second transmission elements each coupled to the drive member and the second component and configured to cause movement of at least one of the first component and the second component in response to movement of the drive member, wherein at least one of the first and second transmission elements includes a first plurality of transmission sub-elements.
 2. The transmission of claim 1, wherein the first and second transmission elements are configured to cause movement of the first component in response to movement of the drive member.
 3. The transmission of claim 2, wherein the first component includes a driven member, and wherein the driven member is unbraked.
 4. The transmission of claim 1, wherein the first and second transmission elements are configured to cause movement of the second component in response to movement of the drive member.
 5. The transmission of claim 4, wherein the second component is unbraked.
 6. The transmission of claim 4, further comprising at least one tensioning mechanism disposed on the second component and configured to apply a tension force to at least one of the first transmission element and the second transmission element and to be adjusted to vary the tension force.
 7. The transmission of claim 1, wherein the first component comprises at least one of an actuator and a pulley.
 8. The transmission of claim 1, wherein the first plurality of transmission sub-elements is configured such that when a tension force is applied to one transmission sub-element of the first plurality of transmission sub-elements an equivalent tension force is applied to another transmission sub-element of the first plurality of transmission sub-elements.
 9. The transmission of claim 1, wherein the first plurality of transmission sub-elements includes a cable having a first connector disposed on a proximal end, a second connector disposed on a distal end, and a third connector disposed between the first and second connectors.
 10. The transmission of claim 1, wherein the first plurality of transmission sub-elements includes first and second cable segments connected to the second component and to a connector, wherein the connector is connected to the drive member.
 11. The transmission of claim 1, wherein the first plurality of transmission sub-elements includes first and second cable segments connected to the drive member and to a connector, wherein the connector is connected to the second component.
 12. The transmission of claim 1, wherein the first plurality of transmission sub-elements includes at least two cables, each cable having a first end connected to the drive member and a second end connected to the second component.
 13. The transmission of claim 1, wherein the first plurality of transmission sub-elements comprises first and second transmission sub-elements, and wherein the drive member includes first and second guides configured to position the first and second transmission sub-elements relative to the drive member.
 14. The transmission of claim 13, wherein the other of the first and second transmission elements includes a second plurality of transmission sub-elements comprising third and fourth transmission sub-elements, and wherein the first and second guides are configured to position the third and fourth transmission sub-elements relative to the drive member.
 15. The transmission of claim 13, wherein the first and second guides extend along a length of the drive member and are adjacent one another along the length of the drive member.
 16. The transmission of claim 12, wherein the first guide comprises a first helical channel and the second guide comprises a second helical channel.
 17. The transmission of claim 13, wherein the first and second guides are congruent.
 18. The transmission of claim 13, wherein the drive member includes a first interface configured to removably secure the first transmission element and a second interface configured to removably secure the second transmission element.
 19. The transmission of claim 1, wherein the first plurality of transmission sub-elements comprises first and second transmission sub-elements, and wherein the transmission includes a guide member configured to maintain a portion of the first transmission sub-element substantially parallel to a portion of the second transmission sub-element.
 20. The transmission of claim 19, wherein the guide member is disposed remotely from the first component.
 21. The transmission of claim 19, wherein the guide member is configured such that there is substantially no relative motion between the guide member and the first plurality of transmission sub-elements in response to movement of the drive member.
 22. The transmission of claim 1, wherein the first transmission element crosses the second transmission element at least once between the coupling of the first transmission element to the drive member and the coupling of the first transmission element to the second component.
 23. The transmission of claim 1, wherein the drive member and at least one of the second component and an intermediate component move via rotation, and an axis of rotation of the drive member is parallel to an axis of rotation of at least one of the second component and the intermediate component, wherein the first and second transmission elements each include a portion in contact with the drive member, a portion in contact with the at least one of the second component and the intermediate component, and a portion therebetween, and wherein the portion therebetween intersects a plane defined by the axis of rotation of the drive member and the axis of rotation of the at least one of the second component and the intermediate component.
 24. The transmission of claim 23, comprising a plurality of intermediate components, wherein the first transmission element and the second transmission element contact each of the plurality of intermediate components between the coupling of the first transmission element to the drive member and the coupling of the first transmission element to the second component. 